Datasheet Evaluation Kit EK-H4

Transcrição

Datasheet Evaluation Kit EK-H4
For SHT7x and SHT2x Humidity and Temperature Sensors





Ready to use Hard and Software
Suitable for data-logging experiments
Programmable Interface
Dew Point and Energy Calculation
Multiple Multiplexer Boxes with Sensors lockable
Product Summary
The evaluation kit EK-H4 is made for running
Sensirion’s humidity and temperature sensors and
display measured values. It is able to communicate
with SHT1x, SHT7x as well as the new generation
SHT2x and display the measurement values on a
display on the multiplexer. The main purpose of the
evaluation kit is demonstrating the unique
performance of Sensirion’s humidity and temperature
sensors without any own hard or software design
work.
In connection with a computer and specific software
supplied with the evaluation kit it may also be used
as a data-logger for simple experimental
measurements. The multiplexer with 4 ports is
connected to the computer via USB interface. The
software may record and display humidity and
temperature values as well as calculated values of
dew point and power consumption. Various
multiplexer boxes with sensors may be run by same
software across various USB interfaces.
Set Up
Material Contents
EK-H4 contains the following components, enclosed in a
handy suitcase:
Figure 1 Schematic of Evaluation Kit EK-H4. Multiplexer box
works without connection to computer but using a power plug.
Optionally, the multiplexer box may be connected to computer
with data-logger software for recording and displaying data
readings.
www.sensirion.com

1 EK-H4 multiplexer box: Providing 4 channels for
sensor cables, one port for power supply cable and
one port for optional USB interface with a computer.
Measured values may be read from a display on the
multiplexer.

4 SHT71 sensors: Pin type sensor with version 4B
sensor chip. Please refer to datasheet SHT7x for
more details.

4 SHT21 sensors: SMD type, DFN 3-0 packaged
sensors with version 4C sensor chip mounted to small
PCB with connector. Please refer to datasheet SHT21
for more details.

4 Sensor cables with RJ45 plug for connecting
sensors with multiplexer box of 3m length.

1 USB cable for connection to computer.

1 Power supply unit with US, EU, AU adapter.

1 Memory Stick with multi viewer software for running EK-H4 as a data-logger.
Device Certification
The Evaluation Kit EK-H4 is RoHS and WEEE compliant.
Version 1.1 – May 2010
1/7
Datasheet EK-H4
Specification
Electrical specification:
EK-H4 Circuit Board
Parameter
min
8
typ
9
max Unit
Input Voltage
10
V
External Supply Input Voltage Ripple
0.5
V
Supply Current
170 280 mA
Input Voltage
4.75 5 5.25 V
USB Supply
Supply Current
170 280 mA
Range
2.1 3.0 3.6
V
0.1
V
Sensor Supply Resolution
Voltage
Accuracy
2
5
%
Output current
40 110 1 mA
Temperature Resolution
11
14 Bit
Humidity Resolution
8
12 Bit
Measurement interval
1
1440 s
Communication USB (via Virtual Com Port (VCP))
Operating
0 – 50°C (multiplexer box)
Temperature
-20 – 70°C (cables, sensor)
4 sensor channels
Display
2 buttons for
display modes
Micro Controller Unit
Debug interface
User field
connected to MCU
USB interface
Reset button
Power supply
Power LED
Default Configuration
Initial configuration set for the default mode (values can be
changed by using the measurement software)
Parameter
Sensor Supply Voltage
Temperature Resolution
Humidity Resolution
Heater
SHT7x
OTP reload
SHT2x
Default value
3.0 V
12 Bit
12 Bit
1s
off
on
off
Power Supply
Used Connection
DC
DC and USB
USB
EK-H4 supplied from
DC (9V)
DC (9V)
USB (5V)
The EK-H4 may be supplied by DC Power Supply Unit at
9V or USB connection at 5V. Power supply by USB is only
possible if USB driver is installed correctly.
+
Table 1
1
EK-H4 Pin Assignment
Pin
Name
Comment
-
GND
Ground
+
Positive
Voltage
9V Supply
8
1
1234
1234
RJ45 Pin
1
Sensor Pin
3
Name
VSS
Description
Ground
3
5
7
1
2
4
SCL
VDD
SDA
Serial clock
Supply voltage
Serial data
Table 2 Pin Assignments: Female RJ45 pin diagram on the
left – SHT21 and SHT71 sensors on the right of the upper panel.
LED Functions
LED
Power LED
RJ45
Connector
DC Power Supply: Pin Diagram
Green LED
Orange LED
Function
LED off denotes low supply
voltage (DC < 8V, USB < 4.75V)
or not connected.
Sensor detected
Measurement is in progress
short circuit current
www.sensirion.com
2/7
EK-H4 Users Guide
1
3
Evaluation Kit Features
The Evaluation Kit EK-H4 may be used as a stand-alone
device, displaying measured values on the screen on the
multiplexer box or – connected to a computer – as a datalogger run by multi-viewer software.
The stand-alone device displays temperature and humidity
values of each connected sensor plus dew-point derived
from the two measured values.
Besides the above mentioned values the data-logger
software displays calculated absolute humidity and power
consumption. Furthermore, supply voltage, sensor
resolution and measurement frequency can be chosen in
a certain range and the on-chip heater may be plugged on
and off. Eventually measured data can be exported for
data processing.
2
Stand-Alone Evaluation Kit
3.1 Getting Started
Set up and application of the stand-alone device is straight
forward:
1.
Select multiplexer box, power supply cable, sensors
with sensor cables as many as needed.
2.
Connect sensors via sensor cables to the multiplexer
box.
3.
Connect multiplexer box via power supply cable to
power (voltage supply also may occur via USB cable
from a computer). Please note: The specific plug
needs to be connected to the power supply cable –
the plastic protection cap on cable side must be
removed before connecting the plug.
4.
As soon as the green LED light is shining, the
measurement starts automatically.
EK-H4 Suitcase
4 Sensor cables
USB cable
Empty
MS
SHT
MS
Adapter plugs
for power
supply cable
Figure 3 Stand-Alone Evaluation Kit. Voltage supply to be set
in the range of AC 80 … 250V.
Multiplexer box
3.2 Display Information
After powering the EK-H4 as standalone measurement
tool the screen shows following information:
Power supply
cable
Sensirion
Evaluation Kit
for SHTxx
EKH4 V1.0
Figure 2 Contents of EK-H4 suitcase: Respective adapter
plug needs to be mounted to power side of power supply cable.
Make sure protective plastic cap on power supply cable is
removed before doing this. MS = Memory Stick with EK-H4
software and datasheets. SHT = humidity and temperature
sensors, SHT71 and SHT21. Sensors are connected to sensor
cables and those to the multiplexer box. USB cable is needed to
connect the multiplexer box to a computer for data-logging
function. One cavity remains empty.
www.sensirion.com
The first screen shows an overview over the connected
sensors. In the first row the sensor number, which can be
matched with the printed number on the cover, is visible.
In the second column the temperature is displayed in °C.
The third column shows the relative humidity. Not
connected sensor ports are displayed with “--.-- ” .
1
2
3
4
25.45°C
--.--°C
24.98°C
25.71°C
45.32%RH
--.--%RH
46.27%RH
45.46%RH
3/7
Datasheet EK-H4
By pressing the buttons the displayed information can be
switched from all sensors to the respective single sensors:
Right button:
Sensor 1 → 2 → 3 → 4 → all → 1
Left button:
Sensor 4 → 3 → 2 → 1 → all → 4
The displayed information by choosing only one sensor is
as following:
Sensor 1:
Temperature:
Humidity RH:
Dew Point:
SHT7x
25.45°C
45.32%
16.76°C
If no sensor is connected to the chosen port sensor
designation is replaced with “no sens”.
To execute a self test for testing the sensor ports and
voltage supply both buttons must be pressed for longer
than one second. For a successful self test each port
requires a sensor to be connected. If no sensor is
connected the corresponding port will show an error.
Sens 1: OK
Sens 2: OK
Sensor Supply
EKH4 Supply
3:
4:
:
:
OK
OK
OK
OK
By pressing one of the buttons the display information will
switch back to the measurement.
4
Data-Logger with Software
Figure 4 EK-H4 configuration with connection to read-out
software on computer. No additional power supply is needed.
4.3 Starting a Measurement
Connect the EK-H4 multiplexer box with a USB cable to
the computer and then start the software by doubleclicking on EKH4Viewer.exe. The connect dialog displays
the COM ports to which EK-H4 multiplexer boxes are
connected – see Figure 5.
After clicking OK, a connection to the multiplexer box is
established and the sensors are listed in the Sensor
Select and Measurement Data sections – see Figure 6.
Using the EK-H4 system as a data-logger requires the
installation of the read-out software on a computer and
connecting multiplexer box and computer via USB cable.
Prior to this a driver installation may be necessary.
4.1 EK-H4 Driver Installation
Connect the EK-H4 multiplexer box to the computer via
USB cable. EK-H4 uses a Silicon Laboratories CP210x
USB to UART bridge controller. If a driver for this controller
is not installed yet, a dialog pops up which helps you to
search for a driver on the internet. Alternatively, the driver
software may be installed from the EK-H4 memory stick.
4.2 Read-Out Software Installation
EK-H4 read-out software requires the .NET framework 2.0
or later. If it is not already installed on the computer, it may
be downloaded from
http://www.microsoft.com/downloads/.
To install the EK-H4 software, simply copy the EK-H4
folder from the memory stick to the hard drive of the
computer.
www.sensirion.com
Figure 5 Connect dialog of read-out software. Window in the
center displays COM ports with multiplexer boxes connected.
4.4 Multiple EK-H4 Devices
EK-H4 read-out software is able to read sensors from
various EK-H4 multiplexers. The different systems are
selected via connect dialog at start-up or using the menu
item File/Connect. To disconnect EK-H4 systems use the
menu item File/Disconnect.
4/7
Datasheet EK-H4
4.6 Calculated Values
Relative humidity and temperature data are measured by
the sensors. From this data dew point and absolute
humidity values are derived.
Power consumption values are calculated based on
sensor type and setting parameters. All these entities may
be displayed in the graphs – to be selected by the menus
at the bottom of the window. Please note: These data are
not measured but simulated.
4.7 Settings
Figure 6 EK-H4 software window before measurement starts.
Sensors are displayed in different colors.
4.5 Temperature and Humidity Measurement
Measurements are started and stopped by the Start/Stop
button. The measured data are displayed in the
Measurement Data table. The measurements which are
displayed in this table can be selected in the context menu
which appears when the right mouse button is clicked on
the table.
Two plots are available, which display the progress of a
measurement over time. The measurement can be
selected in the list below the plot. The scale of the axes
can be altered by pressing the left mouse button on the
axis and moving the mouse. The plot can be dragged
using the left mouse button. The right mouse button can
be used to display a context menu, which offers functions
to print or copy the plot, or to set auto-scale options for the
axes.
The Data Handling section contains controls for settings
which affect all connected sensors. If SHT7x and SHT2x
sensors are connected simultaneously only features from
SHT7x sensors apply. By using only SHT2x sensors the
full range of settings can be used. After disconnection
default configuration is put in place.
Sensor Voltage
Temp. resolution
Humidity resolution
Heater
Table 3
SHT2x
2.1…3.6 V
11, 12, 13, 14 Bit
8, 10, 11, 12 Bit
On, Off
1 … 1440 s
SHT7x
2.1…3.6 V
12, 14 Bit
8, 12 Bit
On, Off
1 … 1440 s
Parameter ranges for the different sensor types.
4.8 Data Logging and Data Export
The data displayed in the measurement plots is kept in
memory. The measured values can be exported to a CSV
file using the menu item File/Export Data. The
measurement data can be cleared with the Clear Data
button. Because the data memory is limited, long-running
measurements should be logged directly to disk. Logging
can be started and stopped using the menu item File/Log
to File.
4.9 Sensor and EK-H4 Properties
Information about the sensors and evaluation kits can be
displayed with the Properties command in the context
menu of the cells in the Sensor Select table.
Figure 7 Software surface during measurement. Displayed
values may be selected via menus at the bottom of the window.
www.sensirion.com
5/7
Datasheet EK-H4
4.10 License Information
The EK-H4 viewer software uses the NPlot charting
library, to which the following license applies:
*************************************************************************
NPlot - A charting library for .NET
Copyright (C) 2003-2006 Matt Howlett and others.
All rights reserved.
Redistribution and use in source and binary forms, with or
without modification, are permitted provided that the following
conditions are met:
1. Redistributions of source code must retain the above
copyright notice, this
list of conditions and the following
disclaimer.
2. Redistributions in binary form must reproduce the above
copyright notice,
this list of conditions and the following
disclaimer in the documentation
and/or other materials
provided with the distribution.
3. Neither the name of NPlot nor the names of its contributors
may be used to endorse or promote products derived from this
software without specific prior written permission.
THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT
HOLDERS AND CONTRIBUTORS "AS IS" AND ANY
EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT
NOT LIMITED TO, THE IMPLIED WARRANTIES OF
MERCHANTABILITY AND FITNESS FOR A PARTICULAR
PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR
ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
EXEMPLARY,
OR
CONSEQUENTIAL
DAMAGES
(INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA,
OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
THE POSSIBILITY OF SUCH DAMAGE.
www.sensirion.com
6/7
Datasheet EK-H4
Revision History
Date
August 2009
May 2010
Version
1.0
1.1
Page(s)
1–7
2
Changes
Initial release
Operating temperature ranges are defined – replacement for storage conditions
Important Notices
Warning, Personal Injury
Do not use this product as safety or emergency stop devices or in
any other application where failure of the product could result in
personal injury. Do not use this product for applications other
than its intended and authorized use. Before installing, handling,
using or servicing this product, please consult the data sheet and
application notes. Failure to comply with these instructions could
result in death or serious injury.
If the Buyer shall purchase or use SENSIRION products for any
unintended or unauthorized application, Buyer shall defend, indemnify
and hold harmless SENSIRION and its officers, employees,
subsidiaries, affiliates and distributors against all claims, costs,
damages and expenses, and reasonable attorney fees arising out of,
directly or indirectly, any claim of personal injury or death associated
with such unintended or unauthorized use, even if SENSIRION shall be
allegedly negligent with respect to the design or the manufacture of the
product.
ESD Precautions
The inherent design of this component causes it to be sensitive to
electrostatic discharge (ESD). To prevent ESD-induced damage and/or
degradation, take customary and statutory ESD precautions when
handling this product.
See application note “ESD, Latchup and EMC” for more information.
Warranty
SENSIRION warrants solely to the original purchaser of this product for
a period of 12 months (one year) from the date of delivery that this
product shall be of the quality, material and workmanship defined in
SENSIRION’s published specifications of the product. Within such
period, if proven to be defective, SENSIRION shall repair and/or
replace this product, in SENSIRION’s discretion, free of charge to the
Buyer, provided that:

notice in writing describing the defects shall be given to
SENSIRION within fourteen (14) days after their appearance;
such defects shall be found, to SENSIRION’s reasonable
satisfaction, to have arisen from SENSIRION’s faulty design,
material, or workmanship;

the defective product shall be returned to SENSIRION’s factory at
the Buyer’s expense; and

the warranty period for any repaired or replaced product shall be
limited to the unexpired portion of the original period.
This warranty does not apply to any equipment which has not been
installed and used within the specifications recommended by
SENSIRION for the intended and proper use of the equipment.
EXCEPT FOR THE WARRANTIES EXPRESSLY SET FORTH
HEREIN, SENSIRION MAKES NO WARRANTIES, EITHER EXPRESS
OR IMPLIED, WITH RESPECT TO THE PRODUCT. ANY AND ALL
WARRANTIES, INCLUDING WITHOUT LIMITATION, WARRANTIES
OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR
PURPOSE, ARE EXPRESSLY EXCLUDED AND DECLINED.
SENSIRION is only liable for defects of this product arising under the
conditions of operation provided for in the data sheet and proper use of
the goods. SENSIRION explicitly disclaims all warranties, express or
implied, for any period during which the goods are operated or stored
not in accordance with the technical specifications.
SENSIRION does not assume any liability arising out of any application
or use of any product or circuit and specifically disclaims any and all
liability, including without limitation consequential or incidental
damages. All operating parameters, including without limitation
recommended parameters, must be validated for each customer’s
applications by customer’s technical experts. Recommended
parameters can and do vary in different applications.
SENSIRION reserves the right, without further notice, (i) to change the
product specifications and/or the information in this document and (ii) to
improve reliability, functions and design of this product.

Copyright© 2009, SENSIRION.
CMOSens® is a trademark of Sensirion
All rights reserved
Headquarter and Sales Offices
Headquarter
SENSIRION AG
Laubisruetistr. 50
CH-8712 Staefa ZH
Switzerland
Phone:
+41 44 306 40 00
Fax:
+41 44 306 40 30
[email protected]
http://www.sensirion.com/
Sales Office USA:
SENSIRION Inc.
2801 Townsgate Rd., Suite 204
Westlake Village, CA 91361
USA
Phone:
+1 805 409 4900
Fax:
+1 805 435 0467
[email protected]
Sales Office Japan:
SENSIRION JAPAN Co. Ltd.
Postal Code: 108-0074
Shinagawa Station Bldg. 7F,
4-23-5, Takanawa, Minato-ku
Tokyo, Japan
www.sensirion.com
Phone:
+81 3 3444 4940
Fax:
+81 3 3444 4939
[email protected]
http://www.sensirion.co.jp
Sales Office Korea:
SENSIRION KOREA Co. Ltd.
#1414, Anyang Construction Tower B/D,
1112-1, Bisan-dong, Anyang-city
Gyeonggi-Province
South Korea
Sales Office China:
Sensirion China Co. Ltd.
Room 2411, Main Tower
Jin Zhong Huan Business Building,
Futian District, Shenzhen,
Postal Code 518048
PR China
Phone:
+82 31 440 9925~27
Fax:
+82 31 440 9927
[email protected]
http://www.sensirion.co.kr
phone:
+86 755 8252 1501
fax:
+86 755 8252 1580
[email protected]
www.sensirion.com.cn
Find your local representative at: http://www.sensirion.com/reps
7/7
Datasheet SHT7x (SHT71, SHT75)
Humidity and Temperature Sensor





Fully calibrated
Digital output
Low power consumption
Excellent long term stability
Pin type package – easy integration
Product Summary
SHT7x (including SHT71 and SHT75) is Sensirion’s family
of relative humidity and temperature sensors with pins.
The sensors integrate sensor elements plus signal
processing in compact format and provide a fully
calibrated digital output. A unique capacitive sensor
element is used for measuring relative humidity while
temperature is measured by a band-gap sensor. The
applied CMOSens® technology guarantees excellent
reliability and long term stability. Both sensors are
seamlessly coupled to a 14bit analog to digital converter
and a serial interface circuit. This results in superior signal
quality, a fast response time and insensitivity to external
disturbances (EMC).
Each SHT7x is individually calibrated in a precision
humidity chamber. The calibration coefficients are
programmed into an OTP memory on the chip. These
coefficients are used to internally calibrate the signals
from the sensors. The 2-wire serial interface and internal
voltage regulation allows for easy and fast system
integration. The small size and low power consumption
makes SHT7x the ultimate choice for even the most
demanding applications.
Dimensions
Sensor Chip
SHT7x is supplied on FR4 with pins which allows for easy
integration or replacement. The same sensor is also
available as surface mountable packaging (SHT1x) or on
flex print (SHTA1).
3.1
2.2
3.7
Ø 0.4
6.4
B2G
13.5
0.6
1.2
19.5
3.7
71
Material Contents
While the sensor is made of a CMOS chip the sensor
housing consists of an LCP cap with epoxy glob top on an
FR4 substrate. Pins are made of a Cu/Be alloy coated with
Ni and Au. The device is fully RoHS and WEEE compliant,
thus it is free of Pb, Cd, Hg, Cr(6+), PBB and PBDE.
1 2 3 4
6.0
3.4
SHT7x V4 – for which this datasheet applies – features a
version 4 Silicon sensor chip. Besides a humidity and a
temperature sensor the chip contains an amplifier, A/D
converter, OTP memory and a digital interface. V4 sensors
can be identified by the alpha-numeric traceability code on
the sensor cap – see example “B2G” code on Figure 1.
Evaluation Kits
0.46
1.27
5.08
0.2
2.0
Figure 1: Drawing of SHT7x (applies to SHT71 and SHT75)
sensor packaging, dimensions in mm (1mm = 0.039inch).
Contact assignment: 1: SCK, 2: VDD, 3: GND, 4: DATA.
Hatched item on backside of PCB is a 100nF capacitor – see
Section 2.1 for more information.
www.sensirion.com
For sensor trial measurements, for qualification of the
sensor or even experimental application (data logging) of
the sensor there is an evaluation kit EK-H4 available
including SHT71 (same sensor chip as SHT1x) and 4
sensor channels, hard and software to interface with a
computer. For other evaluation kits please check
www.sensirion.com/humidity.
1/11
Datasheet SHT7x
Sensor Performance
Relative Humidity12
Parameter
Temperature45
Condition
min
0.4
8
Resolution1
typ
max
typ
max
Accuracy2
SHT71
Accuracy2
SHT75
Units
%RH
bit
%RH
Parameter
1.8
see Figure 2
%RH
Accuracy2
SHT75
0.1
1
%RH
%RH
3
<<1
8
%RH
raw data
linearized
tau 63%
time3
Response
Operating Range
Long term drift4
max
0.05
12
3.0
see Figure 2
Repeatability
Hysteresis
Nonlinearity
typ
0.05
12
0
normal
< 0.5
Condition
Resolution1
typ
max
typ
Accuracy2
SHT71
min
0.04
12
Units
°C
bit
°C
°C
0.3
see Figure 3
max
°C
123.8 °C
254.9 °F
30
s
< 0.04
°C/yr
0.1
Operating Range
Response Time 6
Long term drift
±6
max
0.01
14
0.4
see Figure 3
Repeatability
%RH
s
100 %RH
%RH/yr
typ
0.01
14
tau 63%
-40
-40
5
± 3.0
± 2.5
± 2.0
SHT71
T (°C)
RH (%RH)
±4
±2
SHT75
SHT71
± 1.5
± 1.0
± 0.5
SHT75
± 0.0
±0
0
10
20
30 40 50 60 70
Relative Humidity (%RH)
80
90
-40
100
-20
0
20
40
Temperature (°C)
60
Figure 2: Maximal RH-tolerance at 25°C per sensor type.
Figure 3: Maximal T-tolerance per sensor type.
Electrical and General Items
Packaging Information
Parameter
Source Voltage
Power
Consumption5
Communication
Storage
typ max Units
3.3
5.5
V
sleep
2
5
µW
measuring
3
mW
average
90
µW
digital 2-wire interface, see Communication
10 – 50°C (0 – 80°C peak), 20 – 60%RH
1
Condition
min
2.4
The default measurement resolution of is 14bit for temperature and 12bit for
humidity. It can be reduced to 12/8bit by command to status register.
2 Accuracies are tested at Outgoing Quality Control at 25°C (77°F) and 3.3V.
Values exclude hysteresis and are only applicable to non-condensing
environments.
3 Time for reaching 63% of a step function, valid at 25°C and 1 m/s airflow.
www.sensirion.com
Sensor Type
SHT71
SHT75
Packaging
Tape Stripes
Tape Stripes
Quantity
50
50
80
100
Order Number
1-100092-04
1-100071-04
This datasheet is subject to change and may be
amended without prior notice.
4
Value may be higher in environments with high contents of volatile organic
compounds. See Section 1.3 of Users Guide.
5 Values for VDD=3.3V at 25°C, average value at one 12bit measurement
per second.
6 Response time depends on heat capacity of and thermal resistance to
sensor substrate.
2/11
Users Guide SHT7x
1 Application Information
100
80
Max. Range
Relative Humidity (%)
1.1 Operating Conditions
Sensor works stable within recommended normal range –
see Figure 4. Long term exposures to conditions outside
normal range, especially at humidity >80%RH, may
temporarily offset the RH signal (+3 %RH after 60h). After
return to normal range it will slowly return towards
calibration state by itself. See Section 1.4 “Reconditioning
Procedure” to accelerate eliminating the offset. Prolonged
exposure to extreme conditions may accelerate ageing.
60
40
20
Normal
Range
In manufacturing and transport the sensors shall be
prevented of high concentration of chemical solvents and
long exposure times. Out-gassing of glues, adhesive tapes
and stickers or out-gassing packaging material such as
bubble foils, foams, etc. shall be avoided. Manufacturing
area shall be well ventilated.
For more detailed information please consult the
document “Handling Instructions” or contact Sensirion.
0
-40
For these reasons it is recommended to store the sensors
in original packaging including the sealed ESD bag at
following conditions: Temperature shall be in the range of
10°C – 50°C (0 – 80°C for limited time) and humidity at 20
– 60%RH (sensors that are not stored in ESD bags). For
sensors that have been removed from the original
packaging we recommend to store them in ESD bags
made of metal-in PE-HD8.
-20
0
20
40
60
Temperature (°C)
80
100
120
Figure 4: Operating Conditions
1.2 Sockets and Soldering
For maintain high accuracy specifications the sensor shall
not be soldered. Sockets may be used such as “Preci-dip /
Mill-Max R851-83-004-20-001” or similar.
Standard wave soldering ovens may be used at maximum
235°C for 20 seconds. For manual soldering contact time
must be limited to 5 seconds at up to 350°C7.
After wave soldering the devices should be stored at
>75%RH for at least 12h to allow the polymer to rehydrate. Alternatively the re-hydration process may be
performed at ambient conditions (>40%RH) during more
than 5 days.
In no case, neither after manual nor wave soldering, a
board wash shall be applied. In case of application with
exposure of the sensor to corrosive gases the soldering
pads of pins and PCB shall be sealed to prevent loose
contacts or short cuts.
1.3 Storage Conditions and Handling Instructions
It is of great importance to understand that a humidity
sensor is not a normal electronic component and needs to
be handled with care. Chemical vapors at high
concentration in combination with long exposure times
may offset the sensor reading.
1.4 Reconditioning Procedure
As stated above extreme conditions or exposure to solvent
vapors may offset the sensor. The following reconditioning
procedure may bring the sensor back to calibration state:
Baking:
Re-Hydration:
1.5 Temperature Effects
Relative humidity reading strongly depends on
temperature. Therefore, it is essential to keep humidity
sensors at the same temperature as the air of which the
relative humidity is to be measured. In case of testing or
qualification the reference sensor and test sensor must
show equal temperature to allow for comparing humidity
readings.
The packaging of SHT7x is designed for minimal heat
transfer from the pins to the sensor. Still, if the SHT7x
shares a PCB with electronic components that produce
heat it should be mounted in a way that prevents heat
transfer or keeps it as low as possible.
Furthermore, there are self-heating effects in case the
measurement frequency is too high. Please refer to
Section 3.3 for detailed information.
8
9
7
235°C corresponds to 455°F, 350°C corresponds to 662°F
www.sensirion.com
100 – 105°C at < 5%RH for 10h
20 – 30°C at ~ 75%RH for 12h 9.
For example, 3M antistatic bag, product “1910” with zipper .
75%RH can conveniently be generated with saturated NaCl solution.
100 – 105°C correspond to 212 – 221°F, 20 – 30°C correspond to 68 – 86°F
3/11
For sealing and gluing (use sparingly): Use high filled
epoxy for electronic packaging (e.g. glob top, underfill),
and Silicone. Out-gassing of these materials may also
contaminate the SHT7x (see Section 1.3). Therefore try to
add the sensor as a last manufacturing step to the
assembly, store the assembly well ventilated after
manufacturing or bake at 50°C for 24h to outgas
contaminants before packing.
2.1 Power Pins (VDD, GND)
The supply voltage of SHT7x must be in the range of 2.4
and 5.5V, recommended supply voltage is 3.3V.
Decoupling of VDD and GND by a 100nF capacitor is
integrated on the backside of the sensor packaging.
The serial interface of the SHT7x is optimized for sensor
readout and effective power consumption. The sensor
cannot be addressed by I2C protocol, however, the sensor
can be connected to an I2C bus without interference with
other devices connected to the bus. Microcontroller must
switch between protocols.
SHT7x
(Slave)
1.8 Wiring Considerations and Signal Integrity
SHT7x are often applied using wires. Carrying the SCK
and DATA signal parallel and in close proximity more than
10cm may result in cross talk and loss of communication.
This may be resolved by routing VDD and/or GND
between the two data signals and/or using shielded
cables. Furthermore, slowing down SCK frequency will
possibly improve signal integrity.
Please see the Application Note “ESD, Latch-up and
EMC” for more information.
1.9 ESD (Electrostatic Discharge)
ESD immunity is qualified according to MIL STD 883E,
method 3015 (Human Body Model at 2 kV).
Latch-up immunity is provided at a force current of
100mA with Tamb = 80°C according to JEDEC78A. See
Application Note “ESD, Latch-up and EMC” for more
information.
2 Interface Specifications
Pin
1
2
3
4
Name
SCK
VDD
GND
DATA
Comment
Serial Clock, input only
Source Voltage
Ground
Serial Data, bidirectional
71
Table 1: SHT7x pin assignment.
B2G
71
MicroController
(Master)
DATA
RP
SCK
1 2 3 4
10kΩ
1.7
Materials Used for Sealing / Mounting
Many materials absorb humidity and will act as a buffer
increasing response times and hysteresis. Materials in the
vicinity of the sensor must therefore be carefully chosen.
Recommended materials are: Any metals, LCP, POM
(Delrin), PTFE (Teflon), PE, PEEK, PP, PB, PPS, PSU,
PVDF, PVF.
B2G
1.6 Light
The SHT7x is not light sensitive. Prolonged direct
exposure to sunshine or strong UV radiation may age the
housing.
1 2 3 4
Datasheet SHT7x
VDD
GND
Figure 5: Typical application circuit, including pull up resistor RP.
2.2 Serial clock input (SCK)
SCK is used to synchronize the communication between
microcontroller and SHT7x. Since the interface consists of
fully static logic there is no minimum SCK frequency.
2.3 Serial data (DATA)
The DATA tri-state pin is used to transfer data in and out
of the sensor. For sending a command to the sensor,
DATA is valid on the rising edge of the serial clock (SCK)
and must remain stable while SCK is high. After the falling
edge of SCK the DATA value may be changed. For safe
communication DATA valid shall be extended TSU and THO
before the rising and after the falling edge of SCK,
respectively – see Figure 6. For reading data from the
sensor, DATA is valid TV after SCK has gone low and
remains valid until the next falling edge of SCK.
To avoid signal contention the microcontroller must only
drive DATA low. An external pull-up resistor (e.g. 10 kΩ) is
required to pull the signal high – it should be noted that
pull-up resistors may be included in I/O circuits of
www.sensirion.com
4/11
Datasheet SHT7x
microcontrollers. See Table 2 for detailed I/O characteristic
of the sensor.
Parameter
FSCK SCK Frequency
2.4 Electrical Characteristics
The electrical characteristics such as power consumption,
low and high level, input and output voltages depend on
the supply voltage. Table 2 gives electrical characteristics
of SHT7x with the assumption of 5V supply voltage if not
stated otherwise. For proper communication with the
sensor it is essential to make sure that signal design is
strictly within the limits given in Table 3 and Figure 6.
Absolute maximum ratings for VDD versus GND are +7V
and -0.3V. Exposure to absolute maximum rating
conditions for extended periods may affect the sensor
reliability (e.g. hot carrier degradation, oxide breakdown).
Parameter
Conditions
min
Power supply DC10
2.4
measuring
Supply current
average11
2
sleep
Low level output
IOL < 4 mA
0
voltage
High level output
RP < 25 kΩ
90%
voltage
Low level input
Negative going 0%
voltage
High level input
Positive going 80%
voltage
Input current on
pads
on
Output current
Tri-stated (off)
typ
3.3
0.55
28
0.3
max Units
5.5
V
1
mA
µA
1.5 µA
250
mV
100% VDD
20% VDD
100% VDD
10
1
µA
4
20
mA
µA
Table 2: SHT7x DC characteristics. RP stands for pull up
resistor, while IOL is low level output current.
TSCK
TSCKH
TSCKL
TR
TF
Conditions
min
typ max Units
VDD > 4.5V
0
0.1
5
MHz
VDD < 4.5V
0
0.1
1
MHz
TSCKx SCK hi/low time
100
TR/TF SCK rise/fall time
1
200
*
ns
OL = 5pF
3.5
10
20
ns
OL = 100pF
30
40
200
ns
**
**
**
ns
TFO
DATA fall time
ns
TRO
DATA rise time
TV
DATA valid time
200 250
***
ns
TSU
DATA setup time
100 150
***
ns
THO
DATA hold time
10
****
ns
*
TR_max + TF_max = (FSCK)-1 – TSCKH – TSCKL
**
TR0 is determined by the RP*Cbus time-constant at DATA line
***
TV_max and TSU_max depend on external pull-up resistor (RP) and total bus
line capacitance (Cbus) at DATA line
****
TH0_max < TV – max (TR0, TF0)
15
Table 3: SHT7x I/O signal characteristics, OL stands for Output
Load, entities are displayed in Figure 6.
3 Communication with Sensor
3.1 Start up Sensor
As a first step the sensor is powered up to chosen supply
voltage VDD. The slew rate during power up shall not fall
below 1V/ms. After power-up the sensor needs 11ms to
get to Sleep State. No commands must be sent before
that time.
3.2 Sending a Command
To initiate a transmission, a Transmission Start sequence
has to be issued. It consists of a lowering of the DATA line
while SCK is high, followed by a low pulse on SCK and
raising DATA again while SCK is still high – see Figure 7.
80%
SCK
20%
THO
TSU
DATA valid write
DATA valid read
TV
DATA
SCK
80%
20%
Recommended voltage supply for highest accuracy is 3.3V, due to sensor
calibration.
11 Minimum value with one measurement of 8 bit resolution without OTP reload
per second, typical value with one measurement of 12bit resolution per
second.
www.sensirion.com
20%
TRO
TFO
Figure 6: Timing Diagram, abbreviations are explained in
Table 3. Bold DATA line is controlled by the sensor, plain DATA
line is controlled by the micro-controller. Note that DATA valid
read time is triggered by falling edge of anterior toggle.
10
80%
DATA
80%
20%
Figure 7: "Transmission Start" sequence
The subsequent command consists of three address bits
(only ‘000’ is supported) and five command bits. The
SHT7x indicates the proper reception of a command by
pulling the DATA pin low (ACK bit) after the falling edge of
the 8th SCK clock. The DATA line is released (and goes
high) after the falling edge of the 9th SCK clock.
5/11
Datasheet SHT7x
3.4 Connection reset sequence
If communication with the device is lost the following signal
sequence will reset the serial interface: While leaving
DATA high, toggle SCK nine or more times – see Figure 8.
This must be followed by a Transmission Start sequence
preceding the next command. This sequence resets the
interface only. The status register preserves its content.
www.sensirion.com
Figure 8: Connection Reset Sequence
3.5 CRC-8 Checksum calculation
The whole digital transmission is secured by an 8bit
checksum. It ensures that any wrong data can be detected
and eliminated. As described above this is an additional
feature of which may be used or abandoned. Please
consult Application Note “CRC Checksum” for information
on how to calculate the CRC.
3.6 Status Register
Some of the advanced functions of the SHT7x such as
selecting measurement resolution, end-of-battery notice,
use of OTP reload or using the heater may be activated by
sending a command to the status register. The following
section gives a brief overview of these features.
0 0 0 0 0 1 1 0
Status Register
ACK
After the command Status Register Read or Status
Register Write – see Table 4 – the content of 8 bits of the
status register may be read out or written. For the
communication compare Figure 9 and Figure 10 – the
assignation of the bits is displayed in Table 5.
0 0 0 0 0 1 1 1
Status Register
Checksum
ACK
Figure 9: Status Register Write
Figure 10: Status Register Read
Examples of full communication cycle are displayed in
Figure 11 and Figure 12.
0 0 0 Command
LSB
Wait for
0 0
DATA ready
MSB
ACK
Important: To keep self heating below 0.1°C, SHT7x
should not be active for more than 10% of the time – e.g.
maximum one measurement per second at 12bit accuracy
shall be made.
20%
Checksum
ACK
Communication terminates after the acknowledge bit of
the CRC data. If CRC-8 checksum is not used the
controller may terminate the communication after the
measurement data LSB by keeping ACK high. The device
automatically returns to Sleep Mode after measurement
and communication are completed.
20%
ACK
Bit 7
Two bytes of measurement data and one byte of CRC
checksum (optional) will then be transmitted. The micro
controller must acknowledge each byte by pulling the
DATA line low. All values are MSB first, right justified (e.g.
the 5th SCK is MSB for a 12bit value, for a 8bit result the
first byte is not used).
80%
9
80%
LSb
ACK
After issuing a measurement command (‘00000101’ for
relative humidity, ‘00000011’ for temperature) the
controller has to wait for the measurement to complete.
This takes a maximum of 20/80/320 ms for a 8/12/14bit
measurement. The time varies with the speed of the
internal oscillator and can be lower by up to 30%. To
signal the completion of a measurement, the SHT7x pulls
data line low and enters Idle Mode. The controller must
wait for this Data Ready signal before restarting SCK to
readout the data. Measurement data is stored until
readout, therefore the controller can continue with other
tasks and readout at its convenience.
4-8
DATA
ACK
Bit 7
Measurement of RH and T
3
2
ACK
Bit 7
3.3
2
Transmission Start
TS
Table 4: SHT7x list of commands
SCK 1
TS
Code
0000x
00011
00101
00111
00110
0101x-1110x
11110
TS
Command
Reserved
Measure Temperature
Measure Relative Humidity
Read Status Register
Write Status Register
Reserved
Soft reset, resets the interface, clears the
status register to default values. Wait minimum
11 ms before next command
Figure 11: Overview of Measurement Sequence. TS = Transmission Start, MSB = Most Significant Byte, LSB = Last
Significant Byte, LSb = Last Significant Bit.
6/11
Datasheet SHT7x
Transmission Start
Address = ‘000’
A2
A1
A0
Command = ‘00101’
C3
C2
C1
C0
C4
Measurement (80ms for 12bit)
ACK
SCK
DATA
A2
Idle Bits
14
13
15
12
MSb
11
A1
10
A0
9
8
C4
C3
C2
C1
ACK
C0
12bit Humidity Data
ACK 7
6
5
4
Sensor pulls DATA line low after
completion of measurement
3
2
1
LSb
0
Skip ACK to end transmission (if no CRC is used)
ACK
SCK
DATA
15
14
13
MSb
7
12
6
5
10
11
9
8
CRC-8 Checksum
4
3
2
1
ACK
7
LSb
0
ACK
0
ACK
6
5
4
3
Sleep (wait for next
measurement)
2
1
0
ACK
Transmission Start
SCK
DATA
7
6
5
4
3
2
1
Figure 12: Example RH measurement sequence for value “0000’0100“0011’0001” = 1073 = 35.50%RH (without temperature
compensation). DATA valid times are given and referenced in boxes on DATA line. Bold DATA lines are controlled by sensor while plain
lines are controlled by the micro-controller.
Bit Type Description
Default
7
reserved
0
End of Battery (low voltage
No default value,
detection)
bit is only updated
6 R
X
‘0’ for VDD > 2.47
after a
‘1’ for VDD < 2.47
measurement
5
reserved
0
4
reserved
0
3
For Testing only, do not use 0
2 R/W Heater
0 off
1 R/W no reload from OTP
0 reload
’1’ = 8bit RH / 12bit Temp.
12bit RH
resolution
0 R/W
0
14bit Temp.
resolution
For example the heater can be helpful for functionality
analysis: Humidity and temperature readings before and
after applying the heater are compared. Temperature shall
increase while relative humidity decreases at the same
time. Dew point shall remain the same.
Table 5: Status Register Bits
4 Conversion of Signal Output
Measurement resolution: The default measurement
resolution of 14bit (temperature) and 12bit (humidity) can
be reduced to 12 and 8bit. This is especially useful in high
speed or extreme low power applications.
4.1 Relative Humidity
For compensating non-linearity of the humidity sensor –
see Figure 13 – and for obtaining the full accuracy of the
sensor it is recommended to convert the humidity readout
(SORH) with the following formula with coefficients given in
Table 6:
End of Battery function detects and notifies VDD voltages
below 2.47 V. Accuracy is 0.05 V.
Heater: An on chip heating element can be addressed by
writing a command into status register. The heater may
increase the temperature of the sensor by 5 – 10°C12
beyond ambient temperature. The heater draws roughly
8mA @ 5V supply voltage.
Please note: The temperature reading will display the
temperature of the heated sensor element and not
ambient temperature. Furthermore, the sensor is not
qualified for continuous application of the heater.
OTP reload: With this operation the calibration data is
uploaded to the register before each measurement. This
may be deactivated for reducing measurement time by
about 10ms.
2
RH linear  c 1  c 2  SO RH  c 3  SO RH (%RH)
SORH
12 bit
8 bit
c1
-2.0468
-2.0468
c2
0.0367
0.5872
c3
-1.5955E-6
-4.0845E-4
Table 6: Optimized V4 humidity conversion coefficients
12
Corresponds to 9 – 18°F
www.sensirion.com
7/11
Datasheet SHT7x
The values given in Table 6 are optimized coefficients for
V4 sensors. The parameter set for V3 sensors, which has
been proposed in earlier datasheets, still applies and is
provided by Sensirion upon request. Values higher than
99%RH indicate fully saturated air and must be processed
and displayed as 100%RH13. Please note that the humidity
sensor has no significant voltage dependency.
Relative Humidity
100%
80%
60%
40%
4.4 Dew Point
SHT7x is not measuring dew point directly, however dew
point can be derived from humidity and temperature
readings. Since humidity and temperature are both
measured on the same monolithic chip, the SHT7x allows
superb dew point measurements.
For dew point (Td) calculations there are various formulas
to be applied, most of them quite complicated. For the
temperature range of -40 – 50°C the following
approximation provides good accuracy with parameters
given in Table 10:
20%
0%
0
500
1000
1500
2000
2500
3000
3500
SORH sensor readout (12bit)
Figure 13: Conversion from SORH to relative humidity
4.2 Temperature compensation of Humidity Signal
For temperatures significantly different from 25°C (~77°F)
the humidity signal requires temperature compensation.
The temperature correction corresponds roughly to
0.12%RH/°C @ 50%RH. Coefficients for the temperature
compensation are given in Table 8.
t1
0.01
0.01
t2
0.00008
0.00128
T  d1  d 2  SO T
d1 (°F)
-40.2
-39.6
-39.5
-39.3
-38.9
SOT
14bit
12bit
m
17.62
22.46
Table 9: Parameters for dew point (Td) calculation.
5 Environmental Stability
4.3 Temperature
The band-gap PTAT (Proportional To Absolute
Temperature) temperature sensor is very linear by design.
Use the following formula to convert digital readout (SOT)
to temperature value, with coefficients given in Table 9:
d1 (°C)
-40.1
-39.8
-39.7
-39.6
-39.4
Tn (°C)
243.12
272.62
For more information on dew point calculation see
Application Note “Introduction to Humidity”.
Table 7: Temperature compensation coefficients14
VDD
5V
4V
3.5V
3V
2.5V
Temperature Range
Above water, 0 – 50°C
Above ice,
-40 – 0°C
Please note that “ln(…)” denotes the natural logarithm. For
RH and T the linearized and compensated values for
relative humidity and temperature shall be applied.
RH true  TC  25  t 1  t 2  SO RH   RHlinear
SORH
12 bit
8 bit
 RH  m  T
ln

 100%  Tn  T
Td RH, T   Tn 
 RH  m  T
m  ln

 100%  Tn  T
d2 (°C)
0.01
0.04
d2 (°F)
0.018
0.072
If sensors are qualified for assemblies or devices, please
make sure that they experience same conditions as the
reference sensor. It should be taken into account that
response times in assemblies may be longer, hence
enough dwell time for the measurement shall be granted.
For detailed information please consult Application Note
“Testing Guide”.
SHT7x have been tested according to the test conditions
given in Table 11. Sensor performance under other test
conditions cannot be guaranteed and is not part of the
sensor specifications. Especially, no guarantee can be
given for sensor performance in the field or for customer’s
specific application.
Please contact Sensirion for detailed information.
Table 8: Temperature conversion coefficients15.
13
If wetted excessively (strong condensation of water on sensor surface),
sensor output signal can drop below 100%RH (even below 0%RH in some
cases), but the sensor will recover completely when water droplets
evaporate. The sensor is not damaged by water immersion or condensation.
14 Coefficients apply both to V3 as well as to V4 sensors.
www.sensirion.com
15
Temperature coefficients have slightly been adjusted compared to datasheet
SHTxx version 3.01. Coefficients apply to V3 as well as V4 sensors.
8/11
Datasheet SHT7x
Environment Standard
HTOL
125°C, 1000 h
TC
THU
-40°C - 125°C, 500 cycles
Acc. JESD22-A104-C
85°C / 85%RH, 1000h
Results 16
Within
specifications
Within
specifications
Within
specifications
Qualified
ESD immunity MIL STD 883E, method 3015
(Human Body Model at ±2kV)
Latch-up
force current of ±100mA with Qualified
Tamb = 80°C, acc. JEDEC 17
Lot No.:
Quantity:
RoHS:
XX0-NN-YRRRTTTTT
RRRR
Compliant
Lot No.
Figure 14: First label on reel: XX = Sensor Type (71 for SHT71),
NN = Chip Version (04 for V4), Y = last digit of year, RRR =
number of sensors on reel divided by 10 (200 for 2000 units),
TTTTT = Traceability Code.
Table 10: Qualification tests: HTSL = High Temperature Storage
Lifetime, TC = Temperature Cycles, UHST = Unbiased Highly
accelerated temperature and humidity Test, THU = Temperature
humidity unbiased
Device Type:
6 Packaging
1-100PPP-NN
Description:
6.1 Packaging type
The device is supplied in a single-in-line pin type package.
The sensor housing consists of a Liquid Crystal Polymer
(LCP) cap with epoxy glob top on a standard 0.6 mm FR4
substrate. The sensor head is connected to the pins, by a
small bridge to minimize heat conduction and response
times. The pins are made of Cu/Be alloy coated with
1.3µm Ni and 0.5µm Au, which are soldered to the FR4
substrate by lead-free solder paste. The gold plated back
side of the sensor head is connected to the GND pin. A
100nF capacitor is mounted on the back side between
VDD and GND. The device is fully RoHS and WEEE
compliant – thus it is free of of Pb, Cd, Hg, Cr(6+), PBB
and PBDE.
Size including pins is 19.5 x 5.08 x 3.1mm. Total weight:
168 mg, weight of sensor head: 73 mg.
All pins are Au plated to avoid corrosion. They can be
soldered or mate with most 1.27 mm (0.05’’) sockets, for
example: Preci-dip / Mill-Max R851-83-004-20-001 or
similar.
6.2 Traceability Information
All SHT7x are marked with an alphanumeric, three digit
code on the chip cap (for reference: V3 sensors were
labeled with numeric codes) – see “B2G” on Figure 1. The
lot numbers allow full traceability through production,
calibration and testing. No information can be derived from
the code directly, respective data is stored at Sensirion.
Humidity & Temperature Sensor
SHTxx
Part Order No. 1-100PPP-NN or Customer Number
Date of Delivery: DD.MM.YYYY
Order Code:
45CCCC / 0
Figure 15: Second label on reel: For Device Type and Part
Order Number please refer to Table 12, Delivery Date (also
Date Code) is date of packaging of sensors (DD = day, MM =
month, YYYY = year), CCCC = number of order.
6.3 Shipping Package
SHT7x are shipped in 32mm tape at 50pcs each – for
details see Figure 16 and Table 12. Reels are individually
labeled with barcode and human readable labels, see
section 6.2.
Sensor Type
SHT71
SHT75
Packaging
Tape Stripes
Tape Stripes
Quantity
50
50
Order Number
1-100092-04
1-100071-04
Table 11: Packaging types per sensor type.
Dimensions of packaging tape are given in Figure 16. All
tapes have a 7 pockets empty leader tape (first pockets of
the tape) and a 7 pockets empty trailer tape (last pockets
of the tape).
Labels on the reels are displayed in Figure 14 and Figure
15, they both give traceability information.
16
According to accuracy and long term drift specification given on Page 2.
www.sensirion.com
9/11
2.00 ± 0.10
12.00
4.00
Ø2.0 MIN
Ø1.5 MIN
3.6
2.7
5.6
R0.75 TYP
R0.5 TYP
32.0 ± 0.3
28.4 ± 0.1
0.20± 0.05
20.5
71
14.2
B2G
14.1
R0.30 MAX
6.4
0.30
1.75 ± 0.10
Datasheet SHT7x
Figure 16: Tape configuration and unit orientation within tape,
dimensions in mm (1mm = 0.039inch). Leader tape is to the right
of the figure, trailer tape to the left.
www.sensirion.com
10/11
Datasheet SHT7x
Revision History
Date
March 2007
July 2008
April 2009
May 2010
Version
3.0
4.0
4.2
4.3
Page(s)
1 – 10
1 – 10
2, 7
1 – 11
Changes
Data sheet valid for SHTxx-V4 and SHTxx-V3
New release, rework of datasheet
Amended foot note 2, communication diagram changed (Figure 12)
Errors eliminated, information added – for details please ask for change protocol.
Important Notices
product.
ESD Precautions
Warranty




All rights reserved
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CH-8712 Staefa ZH
Switzerland
Phone:
+41 44 306 40 00
Fax:
+41 44 306 40 30
[email protected]
Sales Office USA:
SENSIRION Inc.
USA
Phone:
+1 805 409 4900
Fax:
+1 805 435 0467
[email protected]
Sales Office Japan:
Tokyo, Japan
www.sensirion.com
Phone:
+81 3 3444 4940
Fax:
+81 3 3444 4939
[email protected]
Sales Office Korea:
Gyeonggi-Province
South Korea
Sales Office China:
Postal Code 518048
PR China
Phone:
+82 31 440 9925~27
Fax:
+82 31 440 9927
[email protected]
phone:
+86 755 8252 1501
fax:
+86 755 8252 1580
[email protected]
11/11
Datasheet SHT21





Fully calibrated
Digital output, I2C interface
DFN type package – reflow solderable
Product Summary
SHT21, the new humidity and temperature sensor of
Sensirion is about to set new standards in terms of size
and intelligence: Embedded in a reflow solderable Dual
Flat No leads (DFN) package of 3 x 3mm foot print and
1.1mm height it provides calibrated, linearized signals in
digital, true I2C format.
With a completely new designed CMOSens® chip, a
reworked capacitive type humidity sensor and an
improved band gap temperature sensor the performance
has been lifted even beyond the outstanding level of the
previous sensor generation (SHT1x and SHT7x). For
example, measures have been taken to stabilize the
behavior at high humidity levels.
Dimensions
Every sensor is individually calibrated and tested. Lot
identification is printed on the sensor and an electronic
identification code is stored on the chip – which can be
read out by command. Furthermore, the resolution of
SHT21 can be changed by command (8/12bit up to
12/14bit for RH/T), low battery can be detected and a
checksum helps to improve communication reliability.
With made improvements and the miniaturization of the
sensor the performance-to-price ratio has been improved
– and eventually, any device should benefit from the
cutting edge energy saving operation mode. For testing
SHT21 a new evaluation Kit EK-H4 is available.
Sensor Chip
3.0
SHT21 features a generation 4C CMOSens® chip.
Besides the capacitive relative humidity sensor and the
band gap temperature sensor, the chip contains an
amplifier, A/D converter, OTP memory and a digital
processing unit.
2.0 typ
1.4 typ
3.0
SHT21
D0AC4
0.3 typ
0.8 typ
0.2
0.3
Bottom View
NC
VDD
SCL
0.75
0.4
Material Contents
1.1
2.2
While the sensor itself is made of Silicon the sensors’
housing consists of a plated Cu lead-frame and green
epoxy-based mold compound. The device is fully RoHS
and WEEE compliant, e.g. free of Pb, Cd and Hg.
1.5
0.4
2.4
1.0
Additional Information and Evaluation Kits
1.0
NC
VSS
SDA
Figure 1: Drawing of SHT21 sensor package, dimensions are
given in mm (1mm = 0.039inch), tolerances are ±0.1mm. NC
and die pad (center pad) are internally connected to VSS. They
may be left floating. VSS = GND, SDA = DATA. Numbering of
E/O pads starts at lower right corner (indicated by notch in die
pad) and goes clockwise (compare Table 2).
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Additional information such as Application Notes is
available from the web page www.sensirion.com/sht21.
For more information please contact Sensirion via
[email protected].
For SHT21 two Evaluation Kits are available: EK-H4, a
four-channel device with Viewer Software, that also serves
for data-logging, and a simple EK-H5 directly connecting
one sensor via USB port to a computer.
1/12
Sensor Performance
Relative Humidity1234
Parameter
Temperature567
Condition
12 bit
8 bit
typ
Resolution 1
Accuracy
tolerance 2
min
typ
0.04
0.7
max
2.0
see Figure 2
max
Repeatability
0.1
Hysteresis
 63%
Operating Range extended 4
Long Term Drift 5
normal
0
%RH
s
100
< 0.5
%RH
%RH
%RH
1
<0.1
8
Nonlinearity
Response time 3
Units
%RH
%RH
%RH
%RH
%RH/yr
Parameter
Condition
14 bit
12 bit
typ
Resolution 1
Accuracy
tolerance 2
min
typ
0.01
0.04
max
0.3
see Figure 3
max
Repeatability
Units
°C
°C
°C
°C
°C
0.1
Operating Range extended 4
Response Time 7
Long Term Drift
 63%
-40
-40
125
257
°C
°F
5
30
s
°C/yr
< 0.04
T (°C)
± 3.0
RH (%RH)
± 10
maximal tolerance
±8
typical tolerance
maximal tolerance
± 2.5
typical tolerance
± 2.0
±6
± 1.5
±4
± 1.0
±2
± 0.5
±0
± 0.0
0
10
20
30
40
50
-40
60 70 80 90 100
-20
0
20
40
60
80
100 120
Temperature (°C)
Figure 2 Typical and maximal tolerance at 25°C for relative
humidity. For extensive information see Users Guide, Sect. 1.2.
Figure 3 Maximal tolerance for temperature sensor in °C.
Electrical Specification
Parameter
Conditions min typ max Units
Supply Voltage, VDD
2.1 3.0 3.6
V
sleep mode
0.15 0.4 µA
Supply Current, IDD 6
measuring
270 300 330 µA
sleep mode
0.5 1.2 µW
6
Power Dissipation
measuring
0.8 0.9 1.0 mW
average 8bit
3.2
µW
VDD = 3.0 V 5.5mW, T = + 0.5-1.5°C
Heater
Communication
digital 2-wire interface, true I2C protocol
Sensor Type
Table 1 Electrical specification. For absolute maximum
values see Section 4.1 of Users Guide.
This datasheet is subject to change and may be amended
without prior notice.
SHT21
Packaging
Tape & Reel
Tape & Reel
Tape & Reel
Quantity
400
1500
5000
Order Number
1-100707-01
1-100645-01
1-100694-01
1
Default measurement resolution is 14bit (temperature) / 12bit (humidity). It can
be reduced to 12/8bit, 11/11bit or 13/10bit by command to user register.
Values exclude hysteresis and long term drift and are applicable to noncondensing environments only.
3 Time for achieving 63% of a step function, valid at 25°C and 1m/s airflow.
4 Normal operating range: 0-80%RH, beyond this limit sensor may read a
reversible offset with slow kinetics (<3%RH after 200hours at 90%RH). For more
details please see Section 1.1 of the Users Guide.
www.sensirion.com
5
Value may be higher in environments with vaporized solvents, out-gassing
tapes, adhesives, packaging materials, etc. For more details please refer to
Handling Instructions.
6 Min and max values of Supply Current and Power Dissipation are based on
fixed VDD = 3.0V and T<60°C. The average value is based on one 8bit
measurement per second.
7 Response time depends on heat conductivity of sensor substrate.
2/12
Datasheet SHT21
Users Guide SHT2x
For details on how Sensirion is specifying and testing
accuracy performance please consult Application Note
“Statement on Sensor Specification”.
1.1 Operating Range
The sensor works stable within recommended Normal
Range – see Figure 4. Long term exposure to conditions
outside Normal Range, especially at humidity >80%RH,
may temporarily offset the RH signal (+3%RH after 60h).
After return into the Normal Range it will slowly return
towards calibration state by itself. See Section 2.3
“Reconditioning Procedure” for eliminating the offset.
Prolonged exposure to extreme conditions may accelerate
ageing.
100
80
60
Normal
Range
40
Please note that above values are maximal tolerances (not
including hysteresis) against a high precision reference
such as a dew point mirror. Typical deviations are at
±2%RH where maximal tolerance is ±3%RH and about
half the maximal tolerance at other values.
1.3 Electrical Specification
Current consumption as given in Table 1 is dependent on
temperature and supply voltage VDD. For estimations on
energy consumption of the sensor Figures 6 and 7 may be
consulted. Please note that values given in these Figures
are of typical nature and the variance is considerable.
Supply Current IDD (µA)
1 Extended Specification
Max.
Range
8
7
6
5
4
3
2
1
0
0
20
20
40
60
80
100
120
Temperature (°C)
0
-40
-20
0
20
40
60
80
100 120
Temperature (°C)
Figure 6 Typical dependency of supply current (sleep mode)
versus temperature at VDD = 3.0V. Please note that the
variance of these data is about ±25% of displayed value.
1.2 RH accuracy at various temperatures
Maximal tolerance for RH accuracy at 25°C is defined in
Figure 2. For other temperatures maximal tolerance has
been evaluated to be within limits displayed in Figure 5.
100
90
80
70
60
50
40
30
20
10
0
±6
±5
±4
±5
±5
±7
±8
Supply Current IDD (nA)
Figure 4 Operating Conditions
20
18
16
14
12
10
8
6
2.1
±4
±6
±3
±5
±3
±4
±5
±3
±5
±4
±6
2.3
2.5
2.7
2.9
3.1
3.3
3.5
Supply Voltage (VDD)
Figure 7 Typical dependency of supply current (sleep mode)
versus supply voltage at 25°C. Please note that deviations may
be up to ±50% of displayed value. Values at 60°C scale with a
factor of about 15 (compare Table 1).
±7
0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80
Temperature (°C)
Figure 5 Maximal tolerance of relative humidity measurements
given in %RH for temperatures 0 – 80°C.
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3/12
Datasheet SHT21
2.1 Soldering Instructions
The DFN’s die pad (centre pad) and perimeter I/O pads
are fabricated from a planar copper lead-frame by overmolding leaving the die pad and I/O pads exposed for
mechanical and electrical connection. Both the I/O pads
and die pad should be soldered to the PCB. In order to
prevent oxidation and optimize soldering, the bottom side
of the sensor pads is plated with Ni/Pd/Au.
On the PCB the I/O lands8 should be 0.2mm longer than
the package I/O pads. Inward corners may be rounded to
match the I/O pad shape. The I/O land width should match
the DFN-package I/O-pads width 1:1 and the land for the
die pad should match 1:1 with the DFN package – see
Figure 8.
The solder mask9 design for the land pattern preferably is
of type Non-Solder Mask Defined (NSMD) with solder
mask openings larger than metal pads. For NSMD pads,
the solder mask opening should be about 120µm to
150µm larger than the pad size, providing a 60µm to 75µm
design clearance between the copper pad and solder
mask. Rounded portions of package pads should have a
matching rounded solder mask-opening shape to minimize
the risk of solder bridging. For the actual pad dimensions,
each pad on the PCB should have its own solder mask
opening with a web of solder mask between adjacent
pads.
0.3
0.2
0.4
0.4
0.7
1.5
Due to the low mounted height of the DFN, “no clean”
type 3 solder paste10 is recommended as well as Nitrogen
purge during reflow.
tP
TP
TL
tL
TS (max)
preheating
critical zone
Time
Figure 9 Soldering profile according to JEDEC standard. TP <=
260°C and tP < 40sec for Pb-free assembly. TL < 220°C and tL <
150sec. Ramp-up/down speeds shall be < 5°C/sec.
It is important to note that the diced edge or side faces of
the I/O pads may oxidise over time, therefore a solder fillet
may or may not form. Hence there is no guarantee for
solder joint fillet heights of any kind.
For soldering SHT2x, standard reflow soldering ovens may
be used. The sensor is qualified to withstand soldering
profile according to IPC/JEDEC J-STD-020D with peak
temperatures at 260°C during up to 40sec for Pb-free
assembly in IR/Convection reflow ovens (see Figure 9).
For manual soldering contact time must be limited to 5
seconds at up to 350°C11.
IMPORTANT: After soldering, the devices should be
stored at >75%RH for at least 12h to allow the sensor
element to re-hydrate. Otherwise the sensor may read an
offset that slowly disappears if exposed to ambient
conditions. Alternatively the re-hydration process may be
performed at ambient conditions (>40%RH) during more
than 5 days.
0.2
2.4
1.0
centered on the thermal land area. It can also be split in
two openings.
Temperature
1.0
Figure 8 Recommended metal land pattern for SHT2x. Values
in mm. Die pad (centre pad) and NC pads may be left floating or
be connected to ground. The outer dotted line represents the
outer dimension of the DFN package.
For solder paste printing a laser-cut, stainless steel stencil
with electro-polished trapezoidal walls and with 0.125mm
stencil thickness is recommended. For the I/O pads the
stencil apertures should be 0.1mm longer than PCB pads
and positioned with 0.1mm offset away from the centre of
the package. The die pad aperture should cover about 70
– 90% of the pad area – say up to 1.4mm x 2.3mm
In no case, neither after manual nor reflow soldering, a
board wash shall be applied. Therefore, and as mentioned
above, it is strongly recommended to use “no-clean” solder
paste. In case of applications with exposure of the sensor
to corrosive gases or condensed water (i.e. environments
with high relative humidity) the soldering pads shall be
sealed (e.g. conformal coating) to prevent loose contacts
or short cuts.
8
The land pattern is understood to be the metal layer on the PCB, onto which
the DFN pads are soldered to.
9 The solder mask is understood to be the insulating layer on top of the PCB
covering the connecting lines.
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10
Solder types are related to the solder particle size in the paste: Type 3 covers
the size range of 25 – 45 µm (powder type 42).
11 260°C = 500°F, 350°C = 662°F
4/12
Datasheet SHT21
Moisture Sensitivity Level (MSL) is 2, according to
IPC/JEDEC J-STD-020D.1; hence storage time is limited
to one year after date of delivery.
For this reason it is recommended to store the sensors in
original packaging including the sealed ESD bag at
10°C – 50°C and humidity at 20 – 60%RH (sensors that
are not stored in ESD bags). For sensors that have been
removed from the original packaging we recommend to
store them in ESD bags made of metal-in PE-HD12.
Baking:
Re-Hydration:
100 – 105°C at < 5%RH for 10h
20 – 30°C at ~ 75%RH for 12h 13.
readings.
If the sensor shares a PCB with electronic components
that produce heat it should be mounted in a way that
prevents heat transfer or keeps it as low as possible.
Measures to reduce heat transfer can be ventilation,
reduction of copper layers between the sensor and the
rest of the PCB or milling a slit into the PCB around the
sensor – see Figure 10.
12
13
measurement frequency is too high. To keep self heating
below 0.1°C, SHT2x should not be active for more than
10% of the time – e.g. maximum two measurements per
second at 12bit accuracy shall be made.
Figure 10 Top view of example of mounted SHT2x with slits
milled into PCB to minimize heat transfer.
2.5 Light
sensor.
2.6 Materials Used for Sealing / Mounting
(Delrin), PTFE (Teflon), PEEK, PP, PB, PPS, PSU, PVDF,
PVF.
contaminate the sensor (see Section 2.2). Therefore try to
manufacturing or bake at >50°C for 24h to outgas
Carrying the SCL and SDA signal parallel and in close
proximity (e.g. in wires) for more than 10cm may result in
cross talk and loss of communication. This may be
resolved by routing VDD and/or VSS between the two
SDA signals and/or using shielded cables. Furthermore,
slowing down SCL frequency will possibly improve signal
integrity. Power supply pins (VDD, VSS) must be
decoupled with a 100nF capacitor – see next Section.
For example, 3M antistatic bag, product “1910” with zipper.
www.sensirion.com
5/12
Datasheet SHT21
of MCUs. See Table 4 and Table 5 for detailed I/O
characteristic of the sensor.
Pin Name
Comment
1 SDA Serial Data, bidirectional
2 VSS Ground
5 VDD Supply Voltage
6 SCL Serial Clock, bidirectional
3,4 NC Not Connected
4
3
5
2
6
1
Table 2 SHT2x pin assignment, NC remain floating (top view)
3.1 Power Pins (VDD, VSS)
The supply voltage of SHT2x must be in the range of 2.1 –
3.6V, recommended supply voltage is 3.0V. Power supply
pins Supply Voltage (VDD) and Ground (VSS) must be
decoupled with a 100nF capacitor, that shall be placed as
close to the sensor as possible – see Figure 11.
3.2 Serial clock (SCL)
SCL is used to synchronize the communication between
microcontroller (MCU) and the sensor. Since the interface
consists of fully static logic there is no minimum SCL
frequency.
3.3 Serial SDA (SDA)
The SDA pin is used to transfer data in and out of the
sensor. For sending a command to the sensor, SDA is
valid on the rising edge of SCL and must remain stable
while SCL is high. After the falling edge of SCL the SDA
value may be changed. For safe communication SDA shall
be valid tSU and tHD before the rising and after the falling
edge of SCL, respectively – see Figure 12. For reading
data from the sensor, SDA is valid tVD after SCL has gone
low and remains valid until the next falling edge of SCL.
VDD
MCU (master)
SCL IN
RP
SHT2x
(slave)
SDA
C = 100nF
SCL
SDA OUT
GND
Figure 11 Typical application circuit, including pull-up resistors
RP and decoupling of VDD and VSS by a capacitor.
To avoid signal contention the micro-controller unit (MCU)
must only drive SDA and SCL low. External pull-up
resistors (e.g. 10kΩ), are required to pull the signal high.
For the choice of resistor size please take bus capacity
requirements into account (compare Table 5). It should be
noted that pull-up resistors may be included in I/O circuits
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4.1 Absolute Maximum Ratings
The electrical characteristics of SHT2x are defined in
Table 1. The absolute maximum ratings as given in Table
3 are stress ratings only and give additional information.
Functional operation of the device at these conditions is
not implied. Exposure to absolute maximum rating
Parameter
VDD to VSS
Digital I/O Pins (SDA, SCL)
to VSS
Input Current on any Pin
min
-0.3
max
5
Units
V
-0.3
VDD + 0.3
V
-100
100
mA
Table 3 Electrical absolute maximum ratings
ESD immunity is qualified according to JEDEC JESD22A114E method (Human Body Model at 4kV), JEDEC
JESD22-A115A method (Machine Model 200V) and
ESDA ESD-STM5.3.1-1999
and
AEC-Q100-011
(Charged Device Model, 750V corner pins, 500V other
pins). Latch-up immunity is provided at a force current of
100mA with Tamb = 125°C according to JEDEC JESD78.
For exposure beyond named limits the sensor needs
additional protection circuit.
4.2 Input / Output Characteristics
low and high level input and output voltages depend on
the supply voltage. For proper communication with the
sensor it is essential to make sure that signal design is
strictly within the limits given in Table 4 & 5 and Figure 12.
RP
SCL OUT
SDA IN
4 Electrical Characteristics
Parameter
Output Low
Voltage, VOL
Output High
Voltage, VOH
Output Sink
Current, IOL
Input Low
Voltage, VIL
Input High
Voltage, VIH
Input Current
Conditions
min
typ
VDD = 3.0 V,
-4 mA < IOL < 0mA
0
-
0.4
V
70%
VDD
-
VDD
V
-
-
-4
mA
0
-
30%
VDD
V
70%
VDD
-
VDD
V
-
-
±1
uA
VDD = 3.6 V,
VIN = 0 V to 3.6 V
max Units
Table 4 DC characteristics of digital input/output pads. VDD =
2.1V to 3.6V, T = -40°C to 125°C, unless otherwise noted.
6/12
Datasheet SHT21
1/fSCL
tSCLH
tR
tSCLL
commands from the master (MCU). Current consumption
during start up is 350µA maximum.
tF
70%
SCL
30%
tSU
SDA valid write
tHD
DATA IN
70%
SDA
30%
SDA valid read
tVD
tF
DATA OUT
70%
SCL
30%
tR
70%
SDA
30%
Figure 12 Timing Diagram for Digital Input/Output Pads,
abbreviations are explained in Table 5. SDA directions are seen
from the sensor. Bold SDA line is controlled by the sensor, plain
SDA line is controlled by the micro-controller. Note that SDA
valid read time is triggered by falling edge of anterior toggle.
Parameter
SCL frequency, fSCL
SCL High Time, tSCLH
SCL Low Time, tSCLL
SDA Set-Up Time, tSU
SDA Hold Time, tHD
SDA Valid Time, tVD
SCL/SDA Fall Time, tF
SCL/SDA Rise Time, tR
Capacitive Load on Bus Line, CB
5.2 Start / Stop Sequence
Each transmission sequence begins with Start condition
(S) and ends with Stop condition (P) as displayed in Figure
13 and Figure 14.
min
0
0.6
1.3
100
0
0
0
0
0
typ
-
max Units
0.4 MHz
µs
µs
ns
900
ns
400
ns
100
ns
300
ns
400
pF
Table 5 Timing specifications of digital input/output pads for I2C
fast mode. Entities are displayed in Figure 12. VDD = 2.1V to
3.6V, T = -40°C to 125°C, unless otherwise noted.
SHT21 communicates with true I2C protocol. For
information on I2C beyond the information in the following
Sections please refer to the following website:
http://www.standardics.nxp.com/support/i2c/.
Please note that all sensors are set to the same I2C
address, as defined in Section 5.3. 14
Furthermore, please note, that Sensirion provides an
exemplary sample code on its home page – compare
www.sensirion.com/sht21.
5.1 Start Up Sensor
As a first step, the sensor is powered up to the chosen
supply voltage VDD (between 2.1V and 3.6V). After
power-up, the sensor needs at most 15ms, while SCL is
high, for reaching idle state, i.e. to be ready accepting
14 For sensors with alternative I2C address please contact Sensirion via
70%
SDA
30%
Figure 13 Transmission Start condition (S) - a high to low
transition on the SDA line while SCL is high. The Start condition
is a unique state on the bus created by the master, indicating to
the slaves the beginning of a transmission sequence (bus is
considered busy after a Start).
70%
SCL
30%
70%
SDA
30%
Figure 14 Transmission Stop condition (P) - a low to high
transition on the SDA line while SCL is high. The Stop condition
is a unique state on the bus created by the master, indicating to
the slaves the end of a transmission sequence (bus is
considered free after a Stop).
After sending the Start condition, the subsequent I2C
header consists of the 7-bit I2C device address ‘1000’000’
and an SDA direction bit (Read R: ‘1’, Write W: ‘0’). The
sensor indicates the proper reception of a byte by pulling
the SDA pin low (ACK bit) after the falling edge of the 8th
SCL clock. After the issue of a measurement command
(‘1110’0011’ for temperature, ‘1110’0101’ for relative
humidity’), the MCU must wait for the measurement to
complete. The basic commands are summarized in Table
6. Hold master or no hold master modes are explained in
next Section.
Command
Trigger T measurement
Trigger RH measurement
Trigger T measurement
Trigger RH measurement
Write user register
Read user register
Soft reset
Comment
hold master
hold master
no hold master
no hold master
Code
1110’0011
1110’0101
1111’0011
1111’0101
1110’0110
1110’0111
1111’1110
Table 6 Basic command set, RH stands for relative humidity,
and T stands for temperature
[email protected].
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7/12
Datasheet SHT21
4
5
6
7
8
S 1 0 0 0 0 0 0 0
I2C
9
10 11 12 13 14 15 16 17 18
1 1 1 1 0 1 0 1
address + write
Command (see Table 6)
Measurement
S 1 0 0 0 0 0 0 1
measuring
I2C address + read
Measurement
S 1 0 0 0 0 0 0 1
continue measuring
5
6
7
8
S 1 0 0 0 0 0 0 0
9
ACK
19 20 21 22 23 24 25 26 27
I2C address + read
28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44
45
0 1 1 0 0 0 1 1
0 1 0 1 0 0 1 0
Data (LSB) Stat.
10 11 12 13 14 15 16 17 18
1 1 1 0 0 1 0 1
I2C address + write
Command (see Table 6)
46 47 48 49 50 51 52 53 54
0 1 1 0 0 0 1 1
NACK
4
ACK
3
ACK
2
NACK
19 20 21 22 23 24 25 26 27
Data (MSB)
1
ACK
3
ACK
2
ACK
In the hold master mode, the SHT2x pulls down the SCL
line while measuring to force the master into a wait state.
By releasing the SCL line the sensor indicates that internal
processing is terminated and that transmission may be
continued.
1
ACK
5.4 Hold / No Hold Master Mode
There are two different operation modes to communicate
with the sensor: Hold Master mode or No Hold Master
mode. In the first case the SCL line is blocked (controlled
by sensor) during measurement process while in the latter
case the SCL line remains open for other communication
while the sensor is processing the measurement. No hold
master mode allows for processing other I2C
communication tasks on a bus while the sensor is
measuring. A communication sequence of the two modes
is displayed in Figure 15 and Figure 16, respectively.
P
Checksum
S 1 0 0 0 0 0 0 1
ACK
19 20 21 22 23 24 25 26 27
35 36 37 38 39 40 41 42 43 44
0 1 1 0 0 0 1 1
ACK
28 29 30 31 32 33 34
Hold during measurement
0 1 0 1 0 0 1 0
Data (MSB)
45
ACK
I2C address + read
Measurement
Data (LSB) Stat.
In the examples given in Figure 15 and Figure 16 the
sensor output is SRH = ‘0110’0011’0101’0000’. For the
calculation of physical values Status Bits must be set to ‘0’
– see Chapter 6.
NACK
46 47 48 49 50 51 52 53 54
0 1 1 0 0 0 1 1
Figure 16 No Hold master communication sequence – grey
blocks are controlled by SHT2x. If measurement is not
completed upon “read” command, sensor does not provide ACK
on bit 27 (more of these iterations are possible). If bit 45 is
changed to NACK followed by Stop condition (P) checksum
transmission is omitted.
P
Checksum
Figure 15 Hold master communication sequence – grey blocks
are controlled by SHT2x. Bit 45 may be changed to NACK
followed by Stop condition (P) to omit checksum transmission.
In no hold master mode, the MCU has to poll for the
termination of the internal processing of the sensor. This is
done by sending a Start condition followed by the I2C
header (1000’0001) as shown in Figure 16. If the internal
processing is finished, the sensor acknowledges the poll of
the MCU and data can be read by the MCU. If the
measurement processing is not finished the sensor
answers no ACK bit and the Start condition must be
issued once more.
For both modes, since the maximum resolution of a
measurement is 14 bit, the two last least significant bits
(LSBs, bits 43 and 44) are used for transmitting status
information. Bit 1 of the two LSBs indicates the
measurement type (‘0’: temperature, ‘1’ humidity). Bit 0 is
currently not assigned.
www.sensirion.com
The maximum duration for measurements depends on the
type of measurement and resolution chosen – values are
displayed in Table 7. Maximum values shall be chosen for
the communication planning of the MCU.
Resolution RH typ RH max
14 bit
13 bit
12 Bit
22
29
11 bit
12
15
10 bit
7
9
8 bit
3
4
T typ
66
33
17
9
T max
85
43
22
11
Units
ms
ms
ms
ms
ms
ms
Table 7 Measurement times for RH and T measurements at
different resolutions. Typical values are recommended for
calculating energy consumption while maximum values shall be
applied for calculating waiting times in communication.
Please note: I2C communication allows for repeated Start
conditions (S) without closing prior sequence with Stop
condition (P) – compare Figures 15, 16 and 18. Still, any
sequence with adjacent Start condition may alternatively
be closed with a Stop condition.
8/12
Datasheet SHT21
8
S 1 0 0 0 0 0 0 0
9
I2C address + write
P
Soft Reset
Description / Coding
Measurement resolution
‘00’
‘01’
‘10’
‘11’
6
1
3, 4, 5
2
1
3
1
1
RH
12 bit
8 bit
10 bit
11 bit
Default
‘00’
T
14 bit
12 bit
13 bit
11 bit
Status: End of battery15
‘0’: VDD > 2.25V
‘1’: VDD < 2.25V
Reserved
Enable on-chip heater
Disable OTP Reload
‘0’
‘0’
‘1’
The end of battery alert is activated when the battery
power falls below 2.25V.
The heater is intended to be used for functionality
diagnosis – relative humidity drops upon rising
temperature. The heater consumes about 5.5mW and
provides a temperature increase of about 0.5 – 1.5°C.
OTP Reload is a safety feature and loads the entire OTP
settings to the register, with the exception of the heater bit,
This status bit is updated after each measurement
www.sensirion.com
9
10 11 12 13 14 15 16 17 18
1 1 1 0 0 1 1 1
ACK
8
Read Register
19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36
0 0 0 0 0 0 1 0
I2C address + read
Register content
37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54
S 1 0 0 0 0 0 0 0
1 1 1 0 0 1 1 0
I2C address + write
55 56 57 58 59 60 61
Write Register
62 63
0 0 0 0 0 0 1 1
P
Register content to be written
Figure 18 Read and write register sequence – grey blocks are
controlled by SHT2x. In this example, the resolution is set to 8bit
/ 12bit.
5.7 CRC Checksum
CRC8 is a well known standard checksum concept. For
implementation please refer to public sources such as
Wikipedia.
5.8 Serial Number
SHT21 provides an electronic identification code. For
instructions on how to read the identification code please
refer to the Application Note “Electronic Identification
Code” – to be downloaded from the web page
www.sensirion.com/SHT21.
Table 8 User Register. Cut-off value for End of Battery signal
may vary by ±0.05V. Reserved bits must not be changed. “OTP
reload” = ‘0’ loads default settings after each time a
measurement command is issued.
15
7
S 1 0 0 0 0 0 0 1
5.6 User Register
The content of User Register is described in Table 8.
Please note that reserved bits must not be changed and
default values of respective reserved bits may change
over time without prior notice. Therefore, for any writing to
the User Register, default values of reserved bits must be
read first. Thereafter, the full User Register string is
composed of respective default values of reserved bits
and the remainder of accessible bits optionally with default
or non-default values.
# Bits
2
6
I2C address + write
Figure 17 Soft Reset – grey blocks are controlled by SHT2x.
Bit
7, 0
5
S 1 0 0 0 0 0 0 0
10 11 12 13 14 15 16 17 18
1 1 1 1 1 1 1 0
4
NACK
7
3
ACK
6
2
ACK
5
1
ACK
4
An example for I2C communication reading and writing the
User Register is given in Figure 18.
ACK
3
ACK
2
ACK
1
before every measurement. This feature is disabled per
default and is not recommended for use. Please use Soft
Reset instead – it contains OTP Reload.
ACK
5.5 Soft Reset
This command (see Table 6) is used for rebooting the
sensor system without switching the power off and on
again. Upon reception of this command, the sensor
system reinitializes and starts operation according to the
default settings – with the exception of the heater bit in the
user register (see Sect. 5.6). The soft reset takes less than
15ms.
Default resolution is set to 12 bit relative humidity and 14
bit temperature reading. Measured data are transferred in
two byte packages, i.e. in frames of 8 bit length where the
most significant bit (MSB) is transferred first (left aligned).
Each byte is followed by an acknowledge bit. The two
status bits, the last bits of LSB, must be set to ‘0’ before
calculating physical values. In the example of Figure 15
and Figure 16, the transferred 16 bit relative humidity data
is ‘0110’0011’0101’0000’ = 25424.
6.1 Relative Humidity Conversion
With the relative humidity signal output SRH the relative
humidity RH is obtained by the following formula (result in
%RH), no matter which resolution is chosen:
9/12
Datasheet SHT21
RH   6  125 
SRH
216
In the example given in Figure 15 and Figure 16 the
relative humidity results to be 42.5%RH.
The physical value RH given above corresponds to the
relative humidity above liquid water according to World
Meteorological Organization (WMO). For relative humidity
above ice RHi the values need to be transformed from
relative humidity above water RHw at temperature t. The
equation is given in the following, compare also
Application Note “Introduction to Humidity:
 β t 
RH i  RH w  exp w 
 λw  t 
 β t 
exp i 
 λi  t 
Units are %RH for relative humidity and °C for
temperature. The corresponding coefficients are defined
as follows: βw = 17.62, λw = 243.12°C, βi = 22.46, λi =
272.62°C.
6.2 Temperature Conversion
The temperature T is calculated by inserting temperature
signal output ST into the following formula (result in °C), no
matter which resolution is chosen:
T   46.85  175.72 
ST
216
The SHT2x sensor series were tested according to AECQ100 Rev. G qualification test method. Sensor
specifications are tested to prevail under the AEC-Q100
temperature grade 2 test conditions listed in Table 916.
Environment Standard
HTOL
125°C, 408 hours
Results17
Within
specifications
TC
-50°C - 125°C, 1000 cycles
Within
specifications
UHST
130°C / 85%RH / ≈2.3bar, 96h Within
specifications
THB
85°C / 85%RH, 1000h
Within
specifications
ESD immunity HBM 4kV, MM 200V, CDM Qualified
750V/500V (corner/other pins)
Latch-up
Tamb = 125°C
Table 9: Performed qualification test series. HTOL = High
Temperature Operating Lifetime, TC = Temperature Cycles,
UHST = Unbiased Highly accelerated Stress Test, THB =
Temperature Humidity Biased. For details on ESD see Sect. 4.1.
16
17
Sensor performance under other test conditions cannot be
guaranteed and is not part of the sensor specifications.
Especially, no guarantee can be given for sensor
performance in the field or for customer’s specific
application.
If sensors are qualified for reliability and behavior in
extreme conditions, please make sure that they
experience same conditions as the reference sensor. It
should be taken into account that response times in
assemblies may be longer, hence enough dwell time for
the measurement shall be granted. For detailed
information please consult Application Note “Testing
Guide”.
8 Packaging
8.1
Packaging Type
SHT2x sensors are provided in DFN packaging (in
analogy with QFN packaging). DFN stands for Dual Flat
No leads.
The sensor chip is mounted to a lead frame made of Cu
and plated with Ni/Pd/Au. Chip and lead frame are over
molded by green epoxy-based mold compound. Please
note that side walls of sensors are diced and hence lead
frame at diced edge is not covered with respective
protective coating. The total weight of the sensor is 25mg.
8.2 Filter Cap and Sockets
For SHT2x a filter cap SF2 will be provided. It is designed
for fast response times and compact size. Please find the
datasheet on Sensirion’s web page.
For testing of SHT2x sensors sockets, such as from
Plastronics, part number 10LQ50S13030
are
recommended (see e.g. www.locknest.com).
All SHT2x are laser marked with an alphanumeric, fivedigit code on the sensor – see Figure 19.
The marking on the sensor consists of two lines with five
digits each. The first line denotes the sensor type
(SHT21). The first digit of the second line defines the
output mode (D = digital, Sensibus and I2C, P = PWM, S =
SDM). The second digit defines the manufacturing year (0
= 2010, 1 = 2011, etc.). The last three digits represent an
alphanumeric tracking code. That code can be decoded by
Sensirion only and allows for tracking on batch level
through production, calibration and testing – and will be
provided upon justified request.
Temperature range is -40 to 105°C (AEC-Q100 temperature grade 2).
According to accuracy and long term drift specification given on Page 2.
www.sensirion.com
10/12
8.0
2.0
4.0
0.3
Ø0.15 MIN
5.5
R0.3 MAX
3.3
12.0
SHT21
D0AC4
Ø0.15 MIN
1.75
Datasheet SHT21
Figure 19 Laser marking on SHT21. For details see text.
1.3
3.3
0.25
Reels are also labeled, as displayed in Figure 20 and
Figure 21, and give additional traceability information.
Lot No.:
Quantity:
RoHS:
R0.25
Figure 22 Sketch of packaging tape and sensor orientation.
Header tape is to the right and trailer tape to the left on this
sketch.
XXO-NN-YRRRTTTTT
RRRR
Compliant
Lot No.
9 Compatibility to SHT1x / 7x protocol
O = Output mode (D = Digital, P = PWM, S = SDM), NN = Chip
Version, Y = last digit of year, RRR = number of sensors on reel
divided by 10 (200 for 2000 units), TTTTT = Traceability Code.
Device Type:
1-100PPP-NN
Description:
SHTxx
Order Code:
46CCCC / 0
SHT2x sensors may be run by communicating with the
Sensirion specific communication protocol used for SHT1x
and SHT7x. In case such protocol is applied please refer
to the communication chapter of datasheet SHT1x or
SHT7x. Please note that reserved status bits of user
register must not be changed.
Please understand that with the SHT1x/7x communication
protocol only functions described in respective datasheets
can be used with the exception of the OTP Reload
function that is not set to default on SHT2x. As an
alternative to OTP Reload the soft reset may be used.
Please note that even if SHT1x/7x protocol is applied the
timing values of Table 5 and Table 7 in this SHT2x
datasheet apply.
For the calculation of physical values the following
equation must be applied:
For relative humidity RH
Order Number (See Packaging Information on page 2), Delivery
Date (also Date Code) is date of packaging of sensors (DD =
day, MM = month, YYYY = year), CCCC = Sensirion order
number.
SHT2x are provided in tape & reel shipment packaging,
sealed into antistatic ESD bags. Standard packaging sizes
are 400, 1500 and 5000 units per reel. For SHT21, each
reel contains 440mm (55 pockets) header tape and
200mm (25 pockets) trailer tape.
RH   6  125 
SRH
2 RES
and for temperature T
T   46.85  175.72 
ST
2 RES
RES is the chosen respective resolution, e.g. 12 (12bit) for
relative humidity and 14 (14bit) for temperature.
The drawing of the packaging tapes with sensor
orientation is shown in Figure 22. The reels are provided in
sealed antistatic bags.
www.sensirion.com
11/12
Datasheet SHT21
Revision History
Date
6 May 2009
21 January 2010
5 May 2010
Version
0.3
1.0
1.1
Page(s)
1–9
1 – 4, 7 – 10
1 – 12
Changes
Initial preliminary release
Complete revision. For complete revision list please require respective document.
Typical specification for temperature sensor. Elimination of errors. For detailed
information, please require complete change list at [email protected].
Important Notices
product.
ESD Precautions
Warranty




Copyright © 2010, by SENSIRION.
All rights reserved
Headquarter
SENSIRION AG
Laubisruetistr. 50
CH-8712 Staefa ZH
Switzerland
Phone:
+41 44 306 40 00
Fax:
+41 44 306 40 30
[email protected]
Sales Office USA:
SENSIRION Inc.
USA
Phone:
+1 805 409 4900
Fax:
+1 805 435 0467
[email protected]
Sales Office Japan:
Tokyo, Japan
www.sensirion.com
Phone:
+81 3 3444 4940
Fax:
+81 3 3444 4939
[email protected]
Sales Office Korea:
Gyeonggi-Province
South Korea
Sales Office China:
Postal Code 518048
PR China
Phone:
+82 31 440 9925~27
Fax:
+82 31 440 9927
[email protected]
phone:
+86 755 8252 1501
fax:
+86 755 8252 1580
[email protected]
12/12
Datasheet SHT1x (SHT10, SHT11, SHT15)





Fully calibrated
Digital output
SMD type package – reflow solderable
Product Summary
Each SHT1x is individually calibrated in a precision
humidity chamber. The calibration coefficients are
programmed into an OTP memory on the chip. These
coefficients are used to internally calibrate the signals
from the sensors. The 2-wire serial interface and internal
voltage regulation allows for easy and fast system
integration. The tiny size and low power consumption
makes SHT1x the ultimate choice for even the most
demanding applications.
Dimensions
Sensor Chip
NC
NC
1
NC
3
4
A5Z
11
Material Contents
NC
NC
2.5 ±0.1
2.2 MAX
2
NC
3.3 ±0.1
2.6 MAX
4.93 ±0.05
0.8 ±0.1
While the sensor is made of a CMOS chip the sensor
housing consists of an LCP cap with epoxy glob top on an
FR4 substrate. The device is fully RoHS and WEEE
compliant, thus it is free of Pb, Cd, Hg, Cr(6+), PBB and
PBDE.
Evaluation Kits
Figure 1: Drawing of SHT1x sensor packaging, dimensions in
mm (1mm = 0.039inch). Sensor label gives “11” for SHT11 as
an example. Contacts are assigned as follows: 1:GND, 2:DATA,
3:SCK, 4:VDD.
www.sensirion.com
SHT1x is supplied in a surface-mountable LCC (Leadless
Chip Carrier) which is approved for standard reflow
soldering processes. The same sensor is also available
with pins (SHT7x) or on flex print (SHTA1).
SHT1x V4 – for which this datasheet applies – features a
version 4 Silicon sensor chip. Besides the humidity and
temperature sensors the chip contains an amplifier, A/D
converter, OTP memory and a digital interface. V4 sensors
can be identified by the alpha-numeric traceability code on
the sensor cap – see example “A5Z” code on Figure 1.
0.6 ±0.1
sensor opening
5.2 ±0.2
4.2 ±0.1
1.27 ±0.05
1.5 ±0.2 2.0 ±0.1 1.5 ±0.1
1.83 ±0.05
7.47 ±0.05
0.95 ±0.1
SHT1x (including SHT10, SHT11 and SHT15) is
Sensirion’s family of surface mountable relative humidity
and temperature sensors. The sensors integrate sensor
elements plus signal processing on a tiny foot print and
provide a fully calibrated digital output. A unique
capacitive sensor element is used for measuring relative
humidity while temperature is measured by a band-gap
sensor. The applied CMOSens® technology guarantees
excellent reliability and long term stability. Both sensors
are seamlessly coupled to a 14bit analog to digital
converter and a serial interface circuit. This results in
superior signal quality, a fast response time and
insensitivity to external disturbances (EMC).
For sensor trial measurements, for qualification of the
sensor or even experimental application (data logging) of
the sensor there is an evaluation kit EK-H4 available
including SHT71 (same sensor chip as SHT1x) and 4
sensor channels, hard and software to interface with a
computer. For other evaluation kits please check
www.sensirion.com/humidity.
1/11
Datasheet SHT1x
Sensor Performance
Relative Humidity123
Parameter
Temperature45
Condition
min
0.4
8
Units
%RH
bit
%RH
Parameter
3.0
see Figure 2
%RH
Accuracy 2
SHT11
2.0
see Figure 2
%RH
Accuracy 2
SHT15
Repeatability
0.1
%RH
Hysteresis
Non-linearity
linearized
3
Response time  (63%)
Operating Range
Long term drift 4 normal
1
<<1
8
%RH
%RH
s
Resolution 1
typical
maximal
typical
maximal
typical
maximal
Accuracy 2
SHT10
Accuracy 2
SHT11
max
0.05
12
4.5
see Figure 2
0
100
< 0.5
%RH
%RH/yr
Accuracy 2
SHT10
± 2.5
±2
typ
0.01
14
see Figure 3
0.1
-40
-40
5
123.8
254.9
30
< 0.04
SHT11
± 1.5
± 1.0
± 0.5
SHT15
±0
°C
°C
°F
s
°C/yr
SHT10
± 2.0
SHT11
maximal
Response Time 6  (63%)
Long term drift
±8
±4
typical
maximal
typical
maximal
typical
max Units
0.01 °C
14
bit
°C
0.5
see Figure 3
°C
0.4
see Figure 3
°C
0.3
Operating Range
± 3.0
SHT10
min
0.04
12
Repeatability
± 10
±6
Condition
Resolution 1
T (°C)
RH (%RH)
Accuracy 2
SHT15
typ
0.05
12
SHT15
± 0.0
0
10
20
30 40 50 60 70
80
90
100
-40
-20
0
20
40
60
Temperature (°C)
Figure 2: Maximal RH-tolerance at 25°C per sensor type.
Figure 3: Maximal T-tolerance per sensor type.
Electrical and General Items
Parameter
Source Voltage
Power
Consumption 5
Communication
Storage
Condition
min
2.4
typ max Units
3.3
5.5
V
sleep
2
5
µW
measuring
3
mW
average
90
µW
digital 2-wire interface, see Communication
10 – 50°C (0 – 125°C peak), 20 – 60%RH
Sensor Type
SHT10
SHT11
SHT15
Packaging
Tape & Reel
Tape & Reel
Tape & Reel
Tape & Reel
Tape & Reel
Tape & Reel
Quantity
2000
100
400
2000
100
400
80
100
Order Number
1-100218-04
1-100051-04
1-100098-04
1-100524-04
1-100085-04
1-100093-04
This datasheet is subject to change and may be
amended without prior notice.
1
The default measurement resolution of is 14bit for temperature and 12bit for
humidity. It can be reduced to 12/8bit by command to status register.
Values exclude hysteresis and are applicable to non-condensing environments
only.
3 Time for reaching 63% of a step function, valid at 25°C and 1 m/s airflow.
www.sensirion.com
4
Value may be higher in environments with high contents of volatile organic
compounds. See Section 1.3 of Users Guide.
5 Values for VDD=3.3V at 25°C, average value at one 12bit measurement
per second.
6 Response time depends on heat capacity of and thermal resistance to
sensor substrate.
2/11
Users Guide SHT1x
100
80
Max. Range
60
40
20
Normal
Range
IMPORTANT: After soldering the devices should be stored
at >75%RH for at least 12h to allow the polymer to rehydrate. Otherwise the sensor may read an offset that
slowly disappears if exposed to ambient conditions.
Alternatively the re-hydration process may be performed at
ambient conditions (>40%RH) during more than 5 days.
In no case, neither after manual nor reflow soldering, a
board wash shall be applied. Therefore it is strongly
recommended to use “no-clean” solder paste. In case of
application with exposure of the sensor to corrosive gases
or condensed water (i.e. environments with high relative
humidity) the soldering pads shall be sealed (e.g.
conformal coating) to prevent loose contacts or short cuts.
For the design of the SHT1x footprint it is recommended to
use dimensions according to Figure 7. Sensor pads are
coated with 35µm Cu, 5µm Ni and 0.1µm Au.
0
0
20
40
60
Temperature (°C)
80
100
2.47
120
1.97
1.07
Figure 4: Operating Conditions
Ø0.60
7.47
1.2 Soldering instructions
For soldering SHT1x standard reflow soldering ovens may
be used. The sensor is qualified to withstand soldering
profile according to IPC/JEDEC J-STD-020D with peak
temperatures at 260°C during up to 40sec including Pbfree assembly in IR/Convection reflow ovens.
1.27 1.27 1.27
-20
1.38
-40
0.80
1.1 Operating Conditions
Sensor works stable within recommended normal range –
see Figure 4. Long term exposures to conditions outside
normal range, especially at humidity >80%RH, may
temporarily offset the RH signal (+3 %RH after 60h). After
return to normal range it will slowly return towards
calibration state by itself. See Section 1.4 “Reconditioning
Procedure” to accelerate eliminating the offset. Prolonged
exposure to extreme conditions may accelerate ageing.
Figure 6: Rear side electrodes of sensor, view from top side.
4.61
preheating
critical zone
Time
Figure 5: Soldering profile according to JEDEC standard. TP <=
260°C and tP < 40sec for Pb-free assembly. TL < 220°C and tL <
150sec. Ramp-up/down speeds shall be < 5°C/sec.
For soldering in Vapor Phase Reflow (VPR) ovens the
peak conditions are limited to TP < 233°C during tP <
60sec and ramp-up/down speeds shall be limited to
10°C/sec. For manual soldering contact time must be
limited to 5 seconds at up to 350°C7.
7
233°C = 451°F, 260°C = 500°F, 350°C = 662°F
www.sensirion.com
1.8
3.48
7.08
1.27 1.27 1.27
No copper in this field
0.47
tL
TS (max)
0.8
Temperature
TL
7.50
tP
TP
1.8
Figure 7: Recommended footprint for SHT1x. Values in mm.
For these reasons it is recommended to store the sensors
in original packaging including the sealed ESD bag at
3/11
Datasheet SHT1x
10°C – 50°C (0 – 125°C for limited time) and humidity at
20 – 60%RH (sensors that are not stored in ESD bags).
For sensors that have been removed from the original
packaging we recommend to store them in ESD bags
made of metal-in PE-HD8.
Baking:
Re-Hydration:
measurement frequency is too high. Please refer to
Section 3.3 for detailed information.
1.6 Light
housing.
1.7 Membranes
SHT1x does not contain a membrane at the sensor
opening. However, a membrane may be added to prevent
dirt and droplets from entering the housing and to protect
the sensor. It will also reduce peak concentrations of
chemical vapors. For optimal response times the air
volume behind the membrane must be kept minimal.
Sensirion recommends and supplies the SF1 filter cap for
optimal IP54 protection (for higher protection – i.e. IP67 SF1 must be sealed to the PCB with epoxy). Please
compare Figure 9.
membrane
100 – 105°C at < 5%RH for 10h
20 – 30°C at ~ 75%RH for 12h 9.
housing
readings.
If the SHT1x shares a PCB with electronic components
that produce heat it should be mounted in a way that
prevents heat transfer or keeps it as low as possible.
Measures to reduce heat transfer can be ventilation,
reduction of copper layers between the SHT1x and the
rest of the PCB or milling a slit into the PCB around the
sensor (see Figure 8).
A5Z
11
Figure 8: Top view of example of mounted SHT1x with slits
milled into PCB to minimize heat transfer.
8
9
For example, 3M antistatic bag, product “1910” with zipper .
www.sensirion.com
o-ring
SHT1x
PCB
Melted plastic pin
Figure 9: Side view of SF1 filter cap mounted between PCB and
housing wall. Volume below membrane is kept minimal.
1.8 Materials Used for Sealing / Mounting
(Delrin), PTFE (Teflon), PE, PEEK, PP, PB, PPS, PSU,
PVDF, PVF.
contaminate the SHT1x (see Section 1.3). Therefore try to
manufacturing or bake at >50°C for 24h to outgas
Carrying the SCK and DATA signal parallel and in close
proximity (e.g. in wires) for more than 10cm may result in
cross talk and loss of communication. This may be
4/11
Datasheet SHT1x
resolved by routing VDD and/or GND between the two
data signals and/or using shielded cables. Furthermore,
slowing down SCK frequency will possibly improve signal
integrity. Power supply pins (VDD, GND) must be
decoupled with a 100nF capacitor if wires are used.
Capacitor should be placed as close to the sensor as
possible. Please see the Application Note “ESD, Latch-up
and EMC” for more information.
1.10 ESD (Electrostatic Discharge)
ESD immunity is qualified according to MIL STD 883E,
method 3015 (Human Body Model at 2 kV).
Latch-up immunity is provided at a force current of
100mA with Tamb = 80°C according to JEDEC78A. See
Application Note “ESD, Latch-up and EMC” for more
information.
Pin Name
Comment
1 GND Ground
2 DATA Serial Data, bidirectional
3 SCK Serial Clock, input only
4 VDD Source Voltage
NC NC Must be left unconnected
NC
1
2
3
4
NC
NC
NC
A5Z
NC
11
NC
Table 1: SHT1x pin assignment, NC remain floating.
2.1 Power Pins (VDD, GND)
The supply voltage of SHT1x must be in the range of 2.4 –
5.5V, recommended supply voltage is 3.3V. Power supply
pins Supply Voltage (VDD) and Ground (GND) must be
decoupled with a 100 nF capacitor – see Figure 10.
The serial interface of the SHT1x is optimized for sensor
readout and effective power consumption. The sensor
cannot be addressed by I2C protocol; however, the sensor
can be connected to an I2C bus without interference with
other devices connected to the bus. The controller must
switch between the protocols.
VDD
GND
RP
10kΩ
SHT1x
MicroController
(Master)
DATA
SCK
A5Z
11
VDD
100nF
2.2 Serial clock input (SCK)
SCK is used to synchronize the communication between
microcontroller and SHT1x. Since the interface consists of
fully static logic there is no minimum SCK frequency.
2.3 Serial data (DATA)
The DATA tri-state pin is used to transfer data in and out
of the sensor. For sending a command to the sensor,
DATA is valid on the rising edge of the serial clock (SCK)
and must remain stable while SCK is high. After the falling
edge of SCK the DATA value may be changed. For safe
communication DATA valid shall be extended TSU and THO
before the rising and after the falling edge of SCK,
respectively – see Figure 11. For reading data from the
sensor, DATA is valid TV after SCK has gone low and
remains valid until the next falling edge of SCK.
To avoid signal contention the microcontroller must only
drive DATA low. An external pull-up resistor (e.g. 10kΩ) is
required to pull the signal high – it should be noted that
pull-up resistors may be included in I/O circuits of
microcontrollers. See Table 2 for detailed I/O characteristic
of the sensor.
2.4 Electrical Characteristics
low and high level input and output voltages depend on
the supply voltage. Table 2 gives electrical characteristics
of SHT1x with the assumption of 5V supply voltage if not
stated otherwise.
Parameter
Conditions
Power supply DC10
measuring
Supply current
average11
sleep
Low level output
IOL < 4 mA
voltage
High level output
RP < 25 kΩ
voltage
Low level input
Negative going
voltage
High level input
Positive going
voltage
Input current on pads
on
Output current
Tri-stated (off)
min
2.4
2
typ max Units
3.3 5.5
V
0.55
1
mA
28
µA
0.3 1.5 µA
0
250
mV
90%
100% VDD
0%
20% VDD
80%
100% VDD
10
1
4
20
µA
mA
µA
Table 2: SHT1x DC characteristics. RP stands for pull up
resistor, while IOL is low level output current.
(Slave)
2.4 – 5.5V
GND
Figure 10: Typical application circuit, including pull up resistor
RP and decoupling of VDD and GND by a capacitor.
www.sensirion.com
10
Recommended voltage supply for highest accuracy is 3.3V, due to sensor
calibration.
11 Minimum value with one measurement of 8bit resolution without OTP reload
per second. Typical value with one measurement of 12bit resolution per
second.
5/11
Datasheet SHT1x
Absolute maximum ratings for VDD versus GND are +7V
and -0.3V. Exposure to absolute maximum rating
For proper communication with the sensor it is essential to
make sure that signal design is strictly within the limits
given in Table 3 and Figure 11.
To initiate a transmission, a Transmission Start sequence
has to be issued. It consists of a lowering of the DATA line
while SCK is high, followed by a low pulse on SCK and
raising DATA again while SCK is still high – see Figure 12.
SCK
TSCK
TSCKH
TSCKL
TR
TF
80%
SCK
20%
TSU
DATA
20%
80%
20%
THO
DATA valid write
Figure 12: "Transmission Start" sequence
DATA valid read
TRO
TFO
TV
80%
DATA
20%
Figure 11: Timing Diagram, abbreviations are explained in
Table 3. Bold DATA line is controlled by the sensor, plain DATA
line is controlled by the micro-controller. Note that DATA valid
read time is triggered by falling edge of anterior toggle.
Parameter
FSCK SCK Frequency
Conditions
min
typ max Units
VDD > 4.5V
0
0.1
5
MHz
VDD < 4.5V
0
0.1
1
MHz
Command
Reserved
Measure Temperature
Measure Relative Humidity
Read Status Register
Write Status Register
Reserved
Soft reset, resets the interface, clears the
status register to default values. Wait minimum
11 ms before next command
100
TR/TF SCK rise/fall time
1
200
*
ns
OL = 5pF
3.5
10
20
ns
OL = 100pF
30
40
200
ns
**
**
**
ns
Table 4: SHT1x list of commands
DATA fall time
ns
The subsequent command consists of three address bits
(only ‘000’ is supported) and five command bits. The
SHT1x indicates the proper reception of a command by
pulling the DATA pin low (ACK bit) after the falling edge of
the 8th SCK clock. The DATA line is released (and goes
high) after the falling edge of the 9th SCK clock.
TSCKx SCK hi/low time
TFO
80%
Code
0000x
00011
00101
00111
00110
0101x-1110x
11110
TRO
DATA rise time
TV
DATA valid time
200 250
***
ns
3.3
TSU
DATA setup time
100 150
***
ns
THO
DATA hold time
10
****
ns
*
TR_max + TF_max = (FSCK)-1 – TSCKH – TSCKL
**
TR0 is determined by the RP*Cbus time-constant at DATA line
***
TV_max and TSU_max depend on external pull-up resistor (RP) and total bus
line capacitance (Cbus) at DATA line
****
TH0_max < TV – max (TR0, TF0)
After issuing a measurement command (‘00000101’ for
relative humidity, ‘00000011’ for temperature) the
controller has to wait for the measurement to complete.
This takes a maximum of 20/80/320 ms for a 8/12/14bit
measurement. The time varies with the speed of the
internal oscillator and can be lower by up to 30%. To
signal the completion of a measurement, the SHT1x pulls
data line low and enters Idle Mode. The controller must
wait for this Data Ready signal before restarting SCK to
readout the data. Measurement data is stored until
readout, therefore the controller can continue with other
tasks and readout at its convenience.
15
Table 3: SHT1x I/O signal characteristics, OL stands for Output
Load, entities are displayed in Figure 11.
3.1 Start up Sensor
As a first step the sensor is powered up to chosen supply
voltage VDD. The slew rate during power up shall not fall
below 1V/ms. After power-up the sensor needs 11ms to
get to Sleep State. No commands must be sent before
that time.
www.sensirion.com
Measurement of RH and T
Two bytes of measurement data and one byte of CRC
checksum (optional) will then be transmitted. The micro
controller must acknowledge each byte by pulling the
DATA line low. All values are MSB first, right justified (e.g.
the 5th SCK is MSB for a 12bit value, for a 8bit result the
first byte is not used).
6/11
Datasheet SHT1x
Important: To keep self heating below 0.1°C, SHT1x
should not be active for more than 10% of the time – e.g.
maximum one measurement per second at 12bit accuracy
shall be made.
After the command Status Register Read or Status
Register Write – see Table 4 – the content of 8 bits of the
status register may be read out or written. For the
communication compare Figure 14 and Figure 15 – the
assignation of the bits is displayed in Table 5.
3
2
2
Status Register
Status Register
ACK
ACK
Bit 7
0 0 0 0 0 1 1 1
ACK
Bit 7
TS
Figure 14: Status Register Write
Checksum
Figure 15: Status Register Read
80%
9
4-8
0 0 0 0 0 1 1 0
Examples of full communication cycle are displayed in
Figure 16 and Figure 17.
20%
Transmission Start
TS
80%
DATA
20%
0 0 0 Command
Wait for
0 0
DATA ready
MSB
ACK
SCK 1
TS
3.4 Connection reset sequence
If communication with the device is lost the following signal
sequence will reset the serial interface: While leaving
DATA high, toggle SCK nine or more times – see Figure
13. This must be followed by a Transmission Start
sequence preceding the next command. This sequence
resets the interface only. The status register preserves its
content.
ACK
3.6 Status Register
Some of the advanced functions of the SHT1x such as
selecting measurement resolution, end-of-battery notice,
use of OTP reload or using the heater may be activated by
sending a command to the status register. The following
section gives a brief overview of these features.
ACK
Bit 7
Communication terminates after the acknowledge bit of
the CRC data. If CRC-8 checksum is not used the
controller may terminate the communication after the
measurement data LSB by keeping ACK high. The device
automatically returns to Sleep Mode after measurement
and communication are completed.
Transmission Start
LSB
Checksum
ACK
3.5 CRC Checksum calculation
The whole digital transmission is secured by an 8bit
checksum. It ensures that any wrong data can be detected
and eliminated. As described above this is an additional
feature of which may be used or abandoned. Please
consult Application Note “CRC Checksum” for information
on how to calculate the CRC.
LSb
ACK
Figure 13: Connection Reset Sequence
Figure 16: Overview of Measurement Sequence. TS = Transmission Start, MSB = Most Significant Byte, LSB = Last
Significant Byte, LSb = Last Significant Bit.
Address = ‘000’
A2
A1 A0
C4
A2
C4
Command = ‘00101’
C3
C2 C1
C0
ACK
Measurement
(80ms for 12bit)
ACK
Sensor pulls DATA line low after
completion of measurement
SCK
DATA
Idle Bits
14
13
15
12
MSb
11
A1
10
A0
9
8
C3
C2
C1
C0
12bit Humidity Data
ACK 7
6
5
4
3
2
1
LSb
0
Skip ACK to end transmission
(if no CRC is used)
ACK
SCK
DATA
15
14
13
MSb
7
12
6
5
10
11
9
ACK
8
CRC-8 Checksum
4
3
2
1
7
LSb
0
ACK
0
ACK
6
5
4
Sleep (wait for next
measurement)
3
2
1
0
ACK
Transmission Start
SCK
DATA
7
6
5
4
3
2
1
Figure 17: Example RH measurement sequence for value “0000’0100“0011’0001” = 1073 = 35.50%RH (without temperature
compensation). DATA valid times are given and referenced in boxes on DATA line. Bold DATA lines are controlled by sensor while plain
lines are controlled by the micro-controller.
www.sensirion.com
7/11
Datasheet SHT1x
Table 5: Status Register Bits
Measurement resolution: The default measurement
resolution of 14bit (temperature) and 12bit (humidity) can
be reduced to 12 and 8bit. This is especially useful in high
speed or extreme low power applications.
End of Battery function detects and notifies VDD voltages
below 2.47V. Accuracy is 0.05V.
Heater: An on chip heating element can be addressed by
writing a command into status register. The heater may
increase the temperature of the sensor by 5 – 10°C12
beyond ambient temperature. The heater draws roughly
8mA @ 5V supply voltage.
For example the heater can be helpful for functionality
analysis: Humidity and temperature readings before and
after applying the heater are compared. Temperature shall
increase while relative humidity decreases at the same
time. Dew point shall remain the same.
Please note: The temperature reading will display the
temperature of the heated sensor element and not
ambient temperature. Furthermore, the sensor is not
qualified for continuous application of the heater.
OTP reload: With this operation the calibration data is
uploaded to the register before each measurement. This
may be deactivated for reducing measurement time by
about 10ms.
4.1 Relative Humidity
For compensating non-linearity of the humidity sensor –
see Figure 18 – and for obtaining the full accuracy of the
sensor it is recommended to convert the humidity readout
12
Corresponds to 9 – 18°F
www.sensirion.com
(SORH) with the following formula with coefficients given in
Table 6:
2
RH linear  c 1  c 2  SO RH  c 3  SO RH (%RH)
SORH
12 bit
8 bit
c1
-2.0468
-2.0468
c2
0.0367
0.5872
c3
-1.5955E-6
-4.0845E-4
Table 6: V4 humidity conversion coefficients
The values given in Table 6 are optimized coefficients for
V4 sensors. The parameter set for V3 sensors, which has
been proposed in earlier datasheets, still applies and is
provided by Sensirion upon request.
Values higher than 99% RH indicate fully saturated air and
must be processed and displayed as 100%RH13. Please
note that the humidity sensor has no significant voltage
dependency.
100%
Relative Humidity
Bit Type Description
Default
7
reserved
0
End of Battery (low voltage
No default value,
detection)
bit is only updated
6 R
X
‘0’ for VDD > 2.47
after a
‘1’ for VDD < 2.47
measurement
5
reserved
0
4
reserved
0
3
For Testing only, do not use 0
2 R/W Heater
0 off
1 R/W no reload from OTP
0 reload
12bit RH
resolution
0 R/W
0
14bit Temp.
resolution
80%
60%
40%
20%
0%
0
500
1000
1500
2000
2500
3000
3500
SORH sensor readout (12bit)
Figure 18: Conversion from SORH to relative humidity
4.2 Temperature compensation of Humidity Signal
For temperatures significantly different from 25°C (~77°F)
the humidity signal requires temperature compensation.
The temperature correction corresponds roughly to
0.12%RH/°C @ 50%RH. Coefficients for the temperature
compensation are given in Table 7.
RH true  TC  25  t 1  t 2  SO RH   RHlinear
SORH
12 bit
8 bit
t1
0.01
0.01
t2
0.00008
0.00128
Table 7: Temperature compensation coefficients14
4.3 Temperature
The band-gap PTAT (Proportional To Absolute
Temperature) temperature sensor is very linear by design.
13
If wetted excessively (strong condensation of water on sensor surface),
sensor output signal can drop below 100%RH (even below 0%RH in some
cases), but the sensor will recover completely when water droplets
evaporate. The sensor is not damaged by water immersion or condensation.
14 Coefficients apply both to V3 as well as to V4 sensors.
8/11
Datasheet SHT1x
Use the following formula to convert digital readout (SOT)
to temperature value, with coefficients given in Table 8:
enough dwell time for the measurement shall be granted.
For detailed information please consult Application Note
“Qualification Guide”.
T  d1  d 2  SO T
The SHT1x sensor series were tested according to AECQ100 Rev. G qualification test method. Sensor
specifications are tested to prevail under the AEC-Q100
temperature grade 2 test conditions listed in Table 1016.
Sensor performance under other test conditions cannot be
guaranteed and is not part of the sensor specifications.
Especially, no guarantee can be given for sensor
performance in the field or for customer’s specific
application.
VDD
5V
4V
3.5V
3V
2.5V
d1 (°C)
-40.1
-39.8
-39.7
-39.6
-39.4
d1 (°F)
-40.2
-39.6
-39.5
-39.3
-38.9
SOT
14bit
12bit
d2 (°C)
0.01
0.04
d2 (°F)
0.018
0.072
Table 8: Temperature conversion coefficients15.
Please contact Sensirion for detailed information.
4.4 Dew Point
SHT1x is not measuring dew point directly, however dew
point can be derived from humidity and temperature
readings. Since humidity and temperature are both
measured on the same monolithic chip, the SHT1x allows
superb dew point measurements.
Environment
HTSL
For dew point (Td) calculations there are various formulas
to be applied, most of them quite complicated. For the
temperature range of -40 – 50°C the following
approximation provides good accuracy with parameters
given in Table 9:
 RH  m  T
ln

 100%  Tn  T
Td RH, T   Tn 
 RH  m  T
m  ln

 100%  Tn  T
Temperature Range
Above water, 0 – 50°C
Above ice,
-40 – 0°C
Tn (°C)
243.12
272.62
Standard
125°C, 1000 hours
Results17
Within
specifications
TC
-50°C - 125°C, 1000 cycles Within
Acc. JESD22-A104-C
specifications
UHST
130°C / 85%RH / ≈2.3bar,
Within
96h
specifications
THU
85°C / 85%RH, 1000h
Within
specifications
ESD immunity MIL STD 883E, method 3015 Qualified
(Human Body Model at ±2kV)
Latch-up
Tamb = 80°C, acc. JEDEC 17
Table 10: Qualification tests: HTSL = High Temperature Storage
Lifetime, TC = Temperature Cycles, UHST = Unbiased Highly
accelerated Stress Test, THB = Temperature Humidity Unbiased
m
17.62
22.46
Table 9: Parameters for dew point (Td) calculation.
Please note that “ln(…)” denotes the natural logarithm. For
RH and T the linearized and compensated values for
relative humidity and temperature shall be applied.
For more information on dew point calculation see
Application Note “Introduction to Humidity”.
If sensors are qualified for assemblies or devices, please
make sure that they experience same conditions as the
reference sensor. It should be taken into account that
response times in assemblies may be longer, hence
6 Packaging
6.1 Packaging type
SHT1x are supplied in a surface mountable LCC
(Leadless Chip Carrier) type package. The sensor housing
consists of a Liquid Crystal Polymer (LCP) cap with epoxy
glob top on a standard 0.8mm FR4 substrate. The device
is fully RoHS and WEEE compliant – it is free of Pb, Cd,
Hg, Cr(6+), PBB and PBDE.
Device size is 7.47 x 4.93 x 2.5 mm (0.29 x 0.19 x 0.1
inch), see Figure 1, weight is 100 mg.
All SHT1x are marked with an alphanumeric, three digit
code on the chip cap (for reference: V3 sensors were
labeled with numeric codes) – see “A5Z” on Figure 1. The
lot numbers allow full traceability through production,
16
15
Temperature coefficients have slightly been adjusted compared to datasheet
SHTxx version 3.01. Coefficients apply to V3 as well as V4 sensors.
www.sensirion.com
Sensor operation temperature range is -40 to 105°C according to AEC-Q100
temperature grade 2.
17 According to accuracy and long term drift specification given on Page 2.
9/11
Datasheet SHT1x
calibration and testing. No information can be derived from
the code directly; respective data is stored at Sensirion
and is provided upon request.
Labels on the reels are displayed in Figures 19 and 20,
they both give traceability information.
Lot No.:
Quantity:
RoHS:
SHT1x are shipped in 12mm tape at 100pcs, 400pcs and
2000pcs – for details see Figure 21 and Table 11. Reels
are individually labeled with barcode and human readable
labels.
Sensor Type
SHT10
XX0-NN-YRRRTTTTT
RRRR
Compliant
SHT11
Lot No.
SHT15
NN = Chip Version (04 for V4), Y = last digit of year, RRR =
number of sensors on reel divided by 10 (200 for 2000 units),
TTTTT = Traceability Code.
Packaging
Tape & Reel
Tape & Reel
Tape & Reel
Tape & Reel
Tape & Reel
Tape & Reel
Quantity
2000
100
400
2000
100
400
Order Number
1-100218-04
1-100051-04
1-100098-04
1-100524-04
1-100085-04
1-100093-04
Table 11: Packaging types per sensor type.
Dimensions of packaging tape are given in Figure 21. All
tapes have a minimum of 480mm empty leader tape (first
pockets of the tape) and a minimum of 300mm empty
trailer tape (last pockets of the tape).
Ø1.50 MIN
1.00
0.30 ± 0.05
Device Type:
12.00
1-100PPP-NN
Description:
R0.3 MAX
11
A5Z
5.80
SHTxx
Order Code:
46CCCC / 0
Ø1.50 MIN
12.0 ± 0.3
5.50 ± 0.05
1.75 ± 0.10
2.00 ± 0.05
R0.5 TYP
2.80
8.20
Order Number please refer to Table 12, Delivery Date (also
Date Code) is date of packaging of sensors (DD = day, MM =
month, YYYY = year), CCCC = Sensirion order number.
www.sensirion.com
Figure 21: Tape configuration and unit orientation within tape,
dimensions in mm (1mm = 0.039inch). The leader tape is at the
right side of the figure while the trailer tape is to the left
(direction of unreeling).
10/11
Datasheet SHT1x
Revision History
Date
July 2008
September 2008
April 2009
May 2010
Version
4.0
4.1
4.2
4.3
Page(s)
1 – 11
3, 4
2, 7
1 – 11
Changes
New release, rework of datasheet
Adjustment of normal operating range and recommendation for antistatic bag
Amended foot note 2, communication diagram updated (Figure 17).
Various errors corrected and additional information given (ask for change protocol).
Important Notices
product.
ESD Precautions
Warranty




All rights reserved
Headquarter
SENSIRION AG
Laubisruetistr. 50
CH-8712 Staefa ZH
Switzerland
Phone:
+41 44 306 40 00
Fax:
+41 44 306 40 30
[email protected]
Sales Office USA:
SENSIRION Inc.
USA
Phone:
+1 805 409 4900
Fax:
+1 805 435 0467
[email protected]
Sales Office Japan:
Tokyo, Japan
www.sensirion.com
Phone:
+81 3 3444 4940
Fax:
+81 3 3444 4939
[email protected]
Sales Office Korea:
Gyeonggi-Province
South Korea
Sales Office China:
Postal Code 518048
PR China
Phone:
+82 31 440 9925~27
Fax:
+82 31 440 9927
[email protected]
phone:
+86 755 8252 1501
fax:
+86 755 8252 1580
[email protected]
11/11

Datasheet Evaluation Kit EK-H4

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