Temperature Sensor IC
Digital output, I2C interface
Low power consumption
Excellent long term stability
DFN type package – reflow solderable
STS21, the new temperature sensor of Sensirion is about Every sensor is individually calibrated and tested. Lot
to set new standards in terms of size and intelligence: identification is printed on the sensor and an electronic
Embedded in a reflow solderable Dual Flat No leads identification code is stored on the chip – which can be
(DFN) package of 3 x 3mm foot print and 1.1mm height it read out by command. Furthermore, the resolution of
provides calibrated, linearized signals in digital, I2C STS21 can be changed by command (11bit up to 14bit),
format. low battery can be detected and a checksum helps to
Using the same CMOSens® technology as Sensirion‟s improve communication reliability.
successful and industry proven SHT2x humidity and With made improvements and the miniaturization of the
temperature sensors, the STS21 offers superior sensor the performance-to-price ratio has been improved
performance and reliability. The ±0.2°C temperature – and eventually, any device should benefit from the
specification allows for implementation of the STS21 in cutting edge energy saving operation mode.
applications with high demands on temperature accuracy.
Dimensions Sensor Chip
3.0 STS21 features a generation 4C CMOSens® chip.
0.3 typ Besides the band gap temperature sensor, the chip
contains an amplifier, A/D converter, OTP memory and a
2.0 typ 1.4 typ 3.0 digital processing unit.
0.8 typ Material Contents
While the sensor itself is made of Silicon the sensors‟
0.2 housing consists of a plated Cu lead-frame and green
Bottom View epoxy-based mold compound. The device is fully RoHS
0.4 0.3 NC VDD SCL and WEEE compliant, e.g. free of Pb, Cd and Hg.
0.4 Additional Information and Evaluation Kits
Additional information such as Application Notes is
available from the web page www.sensirion.com. For more
1.0 1.0 NC VSS SDA information please contact Sensirion via
Figure 1 Drawing of STS21 sensor package, dimensions are For STS21 two Evaluation Kits are available: EK-H4, a
given in mm (1mm = 0.039inch), tolerances are ±0.1mm. The four-channel device with Viewer Software, that also serves
die pad (center pad) is internally connected to VSS. The NC for data-logging, and a simple EK-H5 directly connecting
pads must be left floating. VSS = GND, SDA = DATA. one sensor via USB port to a computer.
Numbering of E/O pads starts at lower right corner (indicated by
notch in die pad) and goes clockwise (compare Table 2).
www.sensirion.com Version 2 – December 2011 1/12
Temperature Specification Electrical Specification
Parameter Condition min typ max Units Parameter Conditions min typ max Units
Resolution1 14 bit 0.01 °C Supply Voltage, VDD 2.1 3.0 3.6 V
12 bit 0.04 °C Supply Current, IDD4 sleep mode 0.15 0.4 µA
Accuracy typ 0.2 °C measuring 200 300 330 µA
tolerance2 max see Figure 2 °C sleep mode 0.5 1.2 µW
Repeatability 0.1 °C Power Dissipation4 measuring 0.6 0.9 1.0 mW
Operating Range extended -40 125 °C average 11bit 8.6 µW
Response Time3 63% 5 30 s Communication digital 2-wire interface, I2C protocol
Long Term Drift < 0.04 °C/yr Table 1 Electrical specification. For absolute maximum
values see Section 4.1 of Users Guide.
± 2.0 Packaging Information
± 1.5 typical tolerance Sensor Type Packaging Quantity Order Number
Tape & Reel 400 1-100811-01
± 1.0 STS21 Tape & Reel 1500 1-100812-01
Tape & Reel 5000 1-100832-01
-40 -20 0 20 40 60 80 100 120
Figure 2 Typical and maximal tolerance for temperature sensor
This datasheet is subject to change and may be amended
1 Default measurement resolution is 14bit. It can be reduced to 13bit, 12bit or without prior notice.
11bit by command to user register.
2 Accuracies are tested at Outgoing Quality Control at 25°C and 3.0V. Values 4 Min and max values of Supply Current and Power Dissipation are based on
exclude long term drift. fixed VDD = 3.0V and T<60°C. The average value is based on one 11bit
3 Response time depends on heat conductivity of sensor substrate. measurement per second.
www.sensirion.com Version 2 – December 2011 2/12
Users Guide STS21
1 Extended Specification 2 Application Information
1.1 Electrical Specification 2.1 Soldering Instructions
Current consumption as given in Table 1 is dependent on The DFN’s die pad (centre pad) and perimeter I/O pads
temperature and supply voltage VDD. For estimations on are fabricated from a planar copper lead-frame by over-
energy consumption of the sensor Figures 3 and 4 may be molding leaving the die pad and I/O pads exposed for
consulted. Please note that values given in these Figures mechanical and electrical connection. Both the I/O pads
are of typical nature and the variance is considerable. and die pad should be soldered to the PCB. In order to
prevent oxidation and optimize soldering, the bottom side
8 of the sensor pads is plated with Ni/Pd/Au.
Supply Current IDD (μA) 7 On the PCB the I/O lands5 should be 0.2mm longer than
6 the package I/O pads. Inward corners may be rounded to
5 match the I/O pad shape. The I/O land width should match
4 the DFN-package I/O-pads width 1:1 and the land for the
3 die pad should match 1:1 with the DFN package – see
2 Figure 5.
1 The solder mask6 design for the land pattern preferably is
0 of type Non-Solder Mask Defined (NSMD) with solder
0 20 40 60 80 100 120 mask openings larger than metal pads. For NSMD pads,
Temperature (°C) the solder mask opening should be about 120μm to
Figure 3 Typical dependency of supply current (sleep mode) 150μm larger than the pad size, providing a 60μm to 75μm
versus temperature at VDD = 3.0V. Please note that the design clearance between the copper pad and solder
variance of these data can be above ±25% of displayed value. 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,
(nA) 20 each pad on the PCB should have its own solder mask
IDD 18 opening with a web of solder mask between adjacent
Current 16 pads.
14 0.4 0.3
10 0.7 0.4
6 1.5 2.4
2.1 2.3 2.5 2.7 2.9 3.1 3.3 3.5
Supply Voltage (VDD) 0.2
Figure 4 Typical dependency of supply current (sleep mode) 1.0 1.0
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 Figure 5 Recommended metal land pattern for STS21. Values
factor of about 15 (compare Table 1). in mm. Die pad (centre pad) may be left floating or be connected
to ground, NC pads shall be left floating. 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
5 The land pattern is understood to be the metal layer on the PCB, onto which
the DFN pads are soldered to.
6 The solder mask is understood to be the insulating layer on top of the PCB
covering the connecting lines.
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the package. The die pad aperture should cover about 70 Furthermore, there are self-heating effects in case the
– 90% of the pad area – say up to 1.4mm x 2.3mm measurement frequency is too high. To keep self heating
centered on the thermal land area. It can also be split in below 0.1°C, STS21 should not be active for more than
two openings. 10% of the time – e.g. maximum two measurements per
Due to the low mounted height of the DFN, “no clean” second at 14bit accuracy shall be made.
type 3 solder paste7 is recommended as well as Nitrogen
purge during reflow.
Temperature TL tL
Figure 7 Top view of example of mounted STS21 with slits
preheating critical zone milled into PCB to minimize heat transfer.
Figure 6 Soldering profile according to JEDEC standard. TP <= 2.4 Light
260°C and tP < 30sec for Pb-free assembly. TL < 220°C and tL < The STS21 is not light sensitive. Prolonged direct
150sec. Ramp-up/down speeds shall be < 5°C/sec. exposure to sunshine or strong UV radiation may age the
It is important to note that the diced edge or side faces of sensor.
the I/O pads may oxidise over time, therefore a solder fillet 2.5 Wiring Considerations and Signal Integrity
may or may not form. Hence there is no guarantee for Carrying the SCL and SDA signal parallel and in close
solder joint fillet heights of any kind. proximity (e.g. in wires) for more than 10cm may result in
For soldering STS21, standard reflow soldering ovens may cross talk and loss of communication. This may be
be used. The sensor is qualified to withstand soldering resolved by routing VDD and/or VSS between the two
profile according to IPC/JEDEC J-STD-020 with peak SDA signals and/or using shielded cables. Furthermore,
temperatures at 260°C during up to 30sec for Pb-free slowing down SCL frequency will possibly improve signal
assembly in IR/Convection reflow ovens (see Figure 6). integrity. Power supply pins (VDD, VSS) must be
For manual soldering contact time must be limited to 5 decoupled with a 100nF capacitor – see next Section.
seconds at up to 350°C.
2.2 Storage Conditions and Handling Instructions 3 Interface Specifications
Moisture Sensitivity Level (MSL) is 1, according to Pin Name Comment
IPC/JEDEC J-STD-020. At the same time, it is 1 SDA Serial Data, bidirectional 4 3
recommended to further process the sensors within 1 year 2 VSS Ground
after date of delivery. 5 VDD Supply Voltage 5 2
During storage, temperature shall be in the range of 10°C 6 SCL Serial Clock, bidirectional 6 1
– 50°C. 3,4 NC Not Connected
2.3 Temperature Effects Table 2 STS21 pin assignment, NC remain floating (top view)
If the sensor shares a PCB with electronic components 3.1 Power Pins (VDD, VSS)
that produce heat it should be mounted in a way that
prevents heat transfer or keeps it as low as possible. The supply voltage of STS21 must be in the range of 2.1 –
Measures to reduce heat transfer can be ventilation, 3.6V, recommended supply voltage is 3.0V. Power supply
reduction of copper layers between the sensor and the pins Supply Voltage (VDD) and Ground (VSS) must be
rest of the PCB or milling a slit into the PCB around the decoupled with a 100nF capacitor, that shall be placed as
sensor – see Figure 7. close to the sensor as possible – see Figure 8.
3.2 Serial clock (SCL)
SCL is used to synchronize the communication between
7 Solder types are related to the solder particle size in the paste: Type 3 covers microcontroller (MCU) and the sensor. Since the interface
the size range of 25 – 45 µm (powder type 42).
www.sensirion.com Version 2 – December 2011 4/12
consists of fully static logic there is no minimum SCL ESD immunity is qualified according to JEDEC JESD22-
frequency. A114 method (Human Body Model at 4kV), JEDEC
JESD22-A115 method (Machine Model 200V) and ESDA
3.3 Serial SDA (SDA) ESD-STM5.3.1-1999 and AEC-Q100-011 (Charged
The SDA pin is used to transfer data in and out of the Device Model, 750V corner pins, 500V other pins). Latch-
sensor. For sending a command to the sensor, SDA is up immunity is provided at a force current of 100mA with
valid on the rising edge of SCL and must remain stable Tamb = 125°C according to JEDEC JESD78. For exposure
while SCL is high. After the falling edge of SCL the SDA beyond named limits the sensor needs additional
value may be changed. For safe communication SDA shall protection circuit.
be valid tSU and tHD before the rising and after the falling
edge of SCL, respectively – see Figure 9. For reading data 4.2 Input / Output Characteristics
from the sensor, SDA is valid tVD after SCL has gone low The electrical characteristics such as power consumption,
and remains valid until the next falling edge of SCL. low and high level input and output voltages depend on
VDD the supply voltage. For proper communication with the
sensor it is essential to make sure that signal design is
MCU (master) RP strictly within the limits given in Table 4 & 5 and Figure 9.
SCL IN SCL Parameter Conditions min typ max Units
SCL OUT STS21 C = 100nF Output Low VDD = 3.0 V, 0 - 0.4 V
(slave) Voltage, VOL -4 mA < IOL < 0mA
SDA IN SDA Output High 70%
SDA OUT Voltage, VOH VDD - VDD V
GND Output Sink - - -4 mA
Figure 8 Typical application circuit, including pull-up resistors Input Low 0 - 30% V
RP and decoupling of VDD and VSS by a capacitor. Voltage, VIL VDD
To avoid signal contention the micro-controller unit (MCU) Input High 70% - VDD V
must only drive SDA and SCL low. External pull-up Voltage, VIH VDD
resistors (e.g. 10kΩ), are required to pull the signal high. Input Current VDD = 3.6 V, - - ±1 uA
VIN = 0 V to 3.6 V
For the choice of resistor size please take bus capacity Table 4 DC characteristics of digital input/output pads. VDD =
requirements into account (compare Table 5). It should be 2.1V to 3.6V, T = -40°C to 125°C, unless otherwise noted.
noted that pull-up resistors may be included in I/O circuits
of MCUs. See Table 4 and Table 5 for detailed I/O 1/fSCL
characteristic of the sensor. tSCLH tSCLL tR tF
4 Electrical Characteristics 30%
4.1 Absolute Maximum Ratings tSU SDA valid write tHD
The electrical characteristics of STS21 are defined in DATA IN
Table 1. The absolute maximum ratings as given in Table SDA 70%
3 are stress ratings only and give additional information. 30%
Functional operation of the device at these conditions is SDA valid read
not implied. Exposure to absolute maximum rating tVD tF tR
conditions for extended periods may affect the sensor DATA OUT
reliability (e.g. hot carrier degradation, oxide breakdown). 30%
Parameter min max Units Figure 9 Timing Diagram for Digital Input/Output Pads,
VDD to VSS -0.3 5 V abbreviations are explained in Table 5. SDA directions are seen
Digital I/O Pins (SDA, SCL) -0.3 VDD + 0.3 V from the sensor. Bold SDA line is controlled by the sensor, plain
to VSS SDA line is controlled by the micro-controller. Note that SDA
Input Current on any Pin -100 100 mA valid read time is triggered by falling edge of anterior toggle.
Table 3 Electrical absolute maximum ratings
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Parameter min typ max Units 30%
SCL frequency, fSCL 0 - 0.4 MHz
SCL High Time, tSCLH 0.6 - - µs 70%
SCL Low Time, tSCLL 1.3 - - µs SDA 30%
SDA Set-Up Time, tSU 100 - - ns Figure 10 Transmission Start condition (S) - a high to low
SDA Hold Time, tHD 0 - 900 ns transition on the SDA line while SCL is high. The Start condition
SDA Valid Time, tVD 0 - 400 ns is a unique state on the bus created by the master, indicating to
SCL/SDA Fall Time, tF 0 - 100 ns the slaves the beginning of a transmission sequence (bus is
considered busy after a Start).
SCL/SDA Rise Time, tR 0 - 300 ns
Capacitive Load on Bus Line, CB 0 - 400 pF SCL 70%
Table 5 Timing specifications of digital input/output pads for I2C 30%
fast mode. Entities are displayed in Figure 9. VDD = 2.1V to
3.6V, T = -40°C to 125°C, unless otherwise noted. For further 70%
information regarding timing, please refer to SDA 30%
Figure 11 Transmission Stop condition (P) - a low to high
5 Communication with Sensor 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
STS21 communicates with I2C protocol. For information on the slaves the end of a transmission sequence (bus is
I2C beyond the information in the following Sections considered free after a Stop).
please refer to the following website: 5.3 Sending a Command
http://www.standardics.nxp.com/support/i2c/. After sending the Start condition, the subsequent I2C
Please note that all sensors are set to the same I2C header consists of the 7-bit I2C device address „1001‟010‟
address, as defined in Section 5.3. 8 and an SDA direction bit (Read R: „1‟, Write W: „0‟). The
Furthermore, please note, that Sensirion provides an sensor indicates the proper reception of a byte by pulling
exemplary sample code for SHT21 sensors on its home the SDA pin low (ACK bit) after the falling edge of the 8th
page – compare www.sensirion.com/SHT21. This sample SCL clock. After the issue of a measurement command,
code can be used for STS21 sensors with minor the MCU must wait for the measurement to complete. The
adjustments (I2C address, no RH measurement). basic commands are summarized in Table 6. Hold master
or no hold master modes are explained in the next
5.1 Start Up Sensor Section.
As a first step, the sensor is powered up to the chosen Command Comment Code
supply voltage VDD (between 2.1V and 3.6V). After Trigger T measurement hold master 1110‟0011
power-up, the sensor needs at most 15ms, while SCL is Trigger T measurement no hold master 1111‟0011
high, for reaching idle state, i.e. to be ready accepting Write user register 1110‟0110
commands from the master (MCU). Current consumption
during start up is 350µA maximum. Whenever the sensor Read user register 1110‟0111
is powered up, but not performing a measurement or Soft reset 1111‟1110
communicating, it is automatically in sleep mode (idle Table 6 Basic command set, T stands for temperature
5.2 Start / Stop Sequence 5.4 Hold / No Hold Master Mode
Each transmission sequence begins with Start condition There are two different operation modes to communicate
(S) and ends with Stop condition (P) as displayed in Figure with the sensor: Hold Master mode or No Hold Master
10 and Figure 11. 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
8 measuring. A communication sequence of the two modes
For sensors with alternative I2C address please contact Sensirion via is displayed in Figure 12 and Figure 13, respectively.
www.sensirion.com Version 2 – December 2011 6/12
In the hold master mode, the STS21 pulls down the SCL 18. Still, any sequence with adjacent Start condition may
line while measuring to force the master into a wait state. alternatively be closed with a Stop condition.
By releasing the SCL line the sensor indicates that internal
processing is terminated and that transmission may be
continued. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 S 1 0 0 1 0 1 0 0 AC K 1 1 1 1 0 0 1 1 AC K
S 1 0 0 1 0 1 0 0 AC K 1 1 1 0 0 0 1 1 AC K I2C address + write Command (see Table 6)
I2C address + write Command (see Table 6) 19 20 21 22 23 24 25 26 27
19 20 21 22 23 24 25 26 27 Measurement S 1 0 0 1 0 1 0 1 NACK
S 1 0 0 1 0 1 0 1 AC K Measurement measuring I2C address + read
I2C address + read Hold during measurement 19 20 21 22 23 24 25 26 27
28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 Measurement S 1 0 0 1 0 1 0 1 AC K
0 1 1 0 0 0 1 1 AC K 0 1 0 1 0 0 0 0 AC K continue measuring I2C address + read
Data (MSB) Data (LSB) Stat. 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45
46 47 48 49 50 51 52 53 54 0 1 1 0 0 0 1 1 AC K 0 1 0 1 0 0 0 0 AC K
0 0 0 0 0 1 1 0 NAC K P Data (MSB) Data (LSB) Stat.
Checksum 46 47 48 49 50 51 52 53 54
Figure 12 Hold master communication sequence – grey blocks 0 0 0 0 0 1 1 0 NACK P
are controlled by STS21. Bit 45 may be changed to NACK Checksum
followed by Stop condition (P) to omit checksum transmission. Figure 13 No Hold master communication sequence – grey
In no hold master mode, the MCU has to poll for the blocks are controlled by STS21. If measurement is not
termination of the internal processing of the sensor. This is completed upon “read” command, sensor does not provide ACK
done by sending a Start condition followed by the I2C on bit 27 (more of these iterations are possible). If bit 45 is
header (1001‟0101) as shown in Figure 13. If the internal changed to NACK followed by Stop condition (P) checksum
processing is finished, the sensor acknowledges the poll of transmission is omitted.
the MCU and data can be read by the MCU. If the Resolution T typ T max Units
measurement processing is not finished the sensor 14 bit 66 85 ms
answers no ACK bit and the Start condition plus header 13 bit 33 43 ms
byte must be issued once more.
For both modes, since the maximum resolution of a 12 Bit 17 22 ms
measurement is 14 bit, the two least significant bits (LSBs, 11 bit 9 11 ms
bits 43 and 44) are used for transmitting status Table 7 Measurement times for T measurements at different
information. Bit 1 of the two LSBs indicates the resolutions. Typical values are recommended for calculating
measurement type („0‟: temperature). Bit 0 is currently not energy consumption while maximum values shall be applied for
assigned. calculating waiting times in communication.
In the examples given in Figure 12 and Figure 13 the 5.5 Soft Reset
sensor output is ST = „0110‟0011‟0101‟0000‟. For the This command (see Table 6) is used for rebooting the
calculation of physical values Status Bits must be set to „0‟ sensor system without switching the power off and on
– see Chapter 6. again. Upon reception of this command, the sensor
The maximum duration for measurements depends on the system reinitializes and starts operation according to the
type of measurement and resolution chosen – values are default settings – with the exception of the heater bit in the
displayed in Table 7. Maximum values shall be chosen for user register (see Sect. 5.6). The soft reset takes less than
the communication planning of the MCU. 15ms.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
Please note: I2C communication allows for repeated Start S 1 0 0 1 0 1 0 0 AC K 1 1 1 1 1 1 1 0 AC K P
conditions (S) without closing prior sequence with Stop
condition (P) – compare Figure 12, Figure 13 and Figure I2C address + write Soft Reset
Figure 14 Soft Reset – grey blocks are controlled by STS21.
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5.6 User Register
The content of User Register is described in Table 8. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
Please note that reserved bits must not be changed and AC K AC K
default values of respective reserved bits may change S 1 0 0 1 0 1 0 0 1 1 1 0 0 1 1 1
over time without prior notice. Therefore, for any writing to I2C address + write Read Register
the User Register, default values of reserved bits must be
read first. Thereafter, the full User Register string is 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36
composed of respective default values of reserved bits S 1 0 0 1 0 1 0 1 AC K 0 0 0 0 0 0 1 0 NACK
and the remainder of accessible bits optionally with default I2C address + read Register content
or non-default values.
37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54
Bit # Bits Description / Coding Default S 1 0 0 1 0 1 0 0 AC K 1 1 1 0 0 1 1 0 AC K
7, 0 2 Measurement resolution „00‟
„00‟ 14 bit I2C address + write Write Register
„01‟ 12 bit 55 56 57 58 59 60 61 62 63
„10‟ 13 bit 0 0 0 0 0 0 1 1 AC K P
„11‟ 11 bit Register content to be written
6 1 Status: End of battery9 „0‟ Figure 15 Read and write register sequence – grey blocks are
„0‟: VDD > 2.25V controlled by STS21. In this example, the resolution is set to
„1‟: VDD < 2.25V 12bit.
3, 4, 5 3 Reserved
2 1 Enable on-chip heater „0‟
1 1 Disable OTP Reload „1‟ 6 Conversion of Signal Output
Table 8 User Register. Threshold value for End of Battery Default resolution is set to 14 bit temperature reading.
signal may vary by ±0.1V. Reserved bits must not be changed. Measured data are transferred in two byte packages, i.e.
“OTP reload” = „0‟ loads default settings after each time a in frames of 8 bit length where the most significant bit
measurement command is issued. (MSB) is transferred first (left aligned). Each byte is
The end of battery alert is activated when the battery followed by an acknowledge bit. The two status bits, the
power falls below 2.25V. last bits of LSB, must be set to „0‟ before calculating
physical values. In the example of Figure 12 and Figure
OTP Reload is a safety feature and loads the entire OTP 13, the transferred 16 bit temperature data is
settings to the register, with the exception of the heater bit, „0110‟0011‟0101‟0000‟ = 25424.
before every measurement. This feature is disabled per
default and is not recommended for use. Please use Soft 6.1 Temperature Conversion
Reset instead – it contains OTP Reload. The temperature T is calculated by inserting temperature
An example for I2C communication reading and writing the signal output ST into the following formula (result in °C), no
User Register is given in Figure 15. matter which resolution is chosen:
5.7 CRC Checksum T 46.85 175.72 ST
STS21 provides a CRC-8 checksum for error detection. 216
The polynomial used is x8 + x5 + x4 +1. For more details 7 Environmental Stability
and implementation please refer to the application note
“CRC Checksum Calculation for SHT2x”. The SHT2x sensor series were tested based on AEC-
5.8 Serial Number Q100 Rev. G qualification test method where applicable.
Sensor specifications are tested to prevail under the AEC-
STS21 provides an electronic identification code. For Q100 temperature grade 2 test conditions listed in Table
instructions on how to read the identification code please 910.
refer to the Application Note “Electronic Identification
Code” – to be downloaded from the web page
9 This status bit is updated after each measurement 10 Temperature range is -40 to 105°C (AEC-Q100 temperature grade 2).
www.sensirion.com Version 2 – December 2011 8/12
Environment Standard Results11 8.3 Traceability Information
HTOL 125°C, 408 hours Within All STS21 are laser marked with an alphanumeric, five-
specifications digit code on the sensor – see Figure 16.
TC -50°C - 125°C, 1000 cycles Within The marking on the sensor consists of two lines with five
specifications digits each. The first line denotes the sensor type (STS21).
UHST 130°C / 85%RH / ≈2.3bar, 96h Within The first digit of the second line defines the output mode
specifications (D = digital, Sensibus and I2C, P = PWM, S = SDM). The
THB 85°C / 85%RH, 1000h Within second digit defines the manufacturing year (0 = 2010, 1 =
specifications 2011, etc.). The last three digits represent an
ESD immunity HBM 4kV, MM 200V, CDM Qualified alphanumeric tracking code. That code can be decoded by
750V/500V (corner/other pins) Sensirion only and allows for tracking on batch level
Latch-up force current of ±100mA with Qualified through production, calibration and testing – and will be
Tamb = 125°C provided upon justified request.
Table 9 Performed qualification test series. HTOL = High
Temperature Operating Lifetime, TC = Temperature Cycles,
UHST = Unbiased Highly accelerated Stress Test, THB = STS21
Temperature Humidity Biased. For details on ESD see Sect. 4.1.
Sensor performance under other test conditions cannot be D0AC4
guaranteed and is not part of the sensor specifications.
Especially, no guarantee can be given for sensor Figure 16 Laser marking on STS21. For details see text.
performance in the field or for customer‟s specific Reels are also labeled, as displayed in Figure 17 and
application. Figure 18, and give additional traceability information.
If sensors are qualified for reliability and behavior in
extreme conditions, please make sure that they Lot No.: OXX-NN-YRRRTTTTT
experience same conditions as the reference sensor. It Quantity: RRRR
should be taken into account that response times in RoHS: Compliant
assemblies may be longer, hence enough dwell time for Lot No.
the measurement shall be granted. For detailed
information please consult Application Note “Testing
Figure 17 First label on reel: O = Output mode (D = Digital), XX
8 Packaging = Sensor Type (21 for STS21), NN = product revision no., Y =
last digit of year, RRR = number of sensors on reel divided by
8.1 Packaging Type 10 (200 for 2000 units), TTTTT = Traceability Code.
STS21 sensors are provided in DFN packaging (in
analogy with QFN packaging). DFN stands for Dual Flat
The sensor chip is mounted to a lead frame made of Cu
and plated with Ni/Pd/Au. Chip and lead frame are over Device Type: 1-100PPP-NN
molded by green epoxy-based mold compound. Please Description: Temperature Sensor STSxx
note that side walls of sensors are diced and hence lead Part Order No. 1-100PPP-NN or Customer Number
frame at diced edge is not covered with respective Date of Delivery: DD.MM.YYYY
protective coating. The total weight of the sensor is 25mg. Order Code: 46CCCC / 0
For testing of STS21 sensors sockets, such as from Figure 18 Second label on reel: For Device Type and Part
Plastronics, part number 10LQ50S13030 are Order Number (See Packaging Information on page 2), Delivery
recommended (see e.g. www.locknest.com). Date (also Date Code) is date of packaging of sensors (DD =
day, MM = month, YYYY = year), CCCC = Sensirion order
11 According to accuracy and long term drift specification given on Page 2.
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8.4 Shipping Package
STS21 are provided in tape & reel shipment packaging,
sealed into antistatic ESD bags. Standard packaging sizes
are 400, 1500 and 5000 units per reel. For STS21, each
reel contains 440mm (55 pockets) header tape and
200mm (25 pockets) trailer tape.
The drawing of the packaging tapes with sensor
orientation is shown in Figure 19. The reels are provided in
sealed antistatic bags.
8.0 Ø0.15 MIN
0.3 4.0 Ø0.15 MIN
R0.3 MAX 5.5
Figure 19 Sketch of packaging tape and sensor orientation.
Header tape is to the right and trailer tape to the left on this
www.sensirion.com Version 2 – December 2011 10/12
Date Version Page(s) Changes
April 2011 0.3 all New preliminary release (based on SHT21 data sheet)
10 June 2011 0.4 2 Quantity of 5000 pcs. added to packaging information
15 July 2011 1 - Initial Release
December 2011 2 1, 2, 4, 6-8 Average power dissipation value, tolerance of threshold value for low battery signal,
minor text adaptations and corrections.
www.sensirion.com Version 2 – December 2011 11/12
Important Notices Warning, Personal Injury
Do not use this product as safety or emergency stop devices or in such defects shall be found, to SENSIRION‟s reasonable
any other application where failure of the product could result in satisfaction, to have arisen from SENSIRION‟s faulty design,
personal injury. Do not use this product for applications other material, or workmanship;
than its intended and authorized use. Before installing, handling, the defective product shall be returned to SENSIRION‟s factory at
using or servicing this product, please consult the data sheet and the Buyer‟s expense; and
application notes. Failure to comply with these instructions could the warranty period for any repaired or replaced product shall be
result in death or serious injury. limited to the unexpired portion of the original period.
This warranty does not apply to any equipment which has not been
If the Buyer shall purchase or use SENSIRION products for any installed and used within the specifications recommended by
unintended or unauthorized application, Buyer shall defend, indemnify SENSIRION for the intended and proper use of the equipment.
and hold harmless SENSIRION and its officers, employees, EXCEPT FOR THE WARRANTIES EXPRESSLY SET FORTH
subsidiaries, affiliates and distributors against all claims, costs, HEREIN, SENSIRION MAKES NO WARRANTIES, EITHER EXPRESS
damages and expenses, and reasonable attorney fees arising out of, OR IMPLIED, WITH RESPECT TO THE PRODUCT. ANY AND ALL
directly or indirectly, any claim of personal injury or death associated WARRANTIES, INCLUDING WITHOUT LIMITATION, WARRANTIES
with such unintended or unauthorized use, even if SENSIRION shall be OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR
allegedly negligent with respect to the design or the manufacture of the PURPOSE, ARE EXPRESSLY EXCLUDED AND DECLINED.
product. SENSIRION is only liable for defects of this product arising under the
ESD Precautions conditions of operation provided for in the data sheet and proper use of
The inherent design of this component causes it to be sensitive to the goods. SENSIRION explicitly disclaims all warranties, express or
electrostatic discharge (ESD). To prevent ESD-induced damage and/or implied, for any period during which the goods are operated or stored
degradation, take customary and statutory ESD precautions when not in accordance with the technical specifications.
handling this product. SENSIRION does not assume any liability arising out of any application
See application note “ESD, Latchup and EMC” for more information. or use of any product or circuit and specifically disclaims any and all
liability, including without limitation consequential or incidental
Warranty damages. All operating parameters, including without limitation
SENSIRION warrants solely to the original purchaser of this product for recommended parameters, must be validated for each customer‟s
a period of 12 months (one year) from the date of delivery that this applications by customer‟s technical experts. Recommended
product shall be of the quality, material and workmanship defined in parameters can and do vary in different applications.
SENSIRION‟s published specifications of the product. Within such SENSIRION reserves the right, without further notice, (i) to change the
period, if proven to be defective, SENSIRION shall repair and/or product specifications and/or the information in this document and (ii) to
replace this product, in SENSIRION‟s discretion, free of charge to the improve reliability, functions and design of this product.
Buyer, provided that: Copyright © 2011, by SENSIRION.
notice in writing describing the defects shall be given to CMOSens® is a trademark of Sensirion
SENSIRION within fourteen (14) days after their appearance; All rights reserved
Headquarters and Subsidiaries
SENSIRION AG Sensirion Inc., USA Sensirion Korea Co. Ltd.
Laubisruetistr. 50 phone: +1 805 409 4900 phone: +82 31 345 0031 3
CH-8712 Staefa ZH firstname.lastname@example.org email@example.com
Switzerland www.sensirion.com www.sensirion.co.kr
phone: +41 44 306 40 00 Sensirion Japan Co. Ltd. Sensirion China Co. Ltd.
fax: +41 44 306 40 30 phone: +81 3 3444 4940 phone: +86 755 8252 1501
firstname.lastname@example.org email@example.com firstname.lastname@example.org
www.sensirion.com www.sensirion.co.jp www.sensirion.com.cn
Sensirion AG (Germany)
phone: +41 44 927 11 66
www.sensirion.com To find your local representative, please visit www.sensirion.com/contact
www.sensirion.com Version 2 – December 2011 12/12
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