SHT21

SHT21 SENSITRON | Alldatasheet

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www.sensirion.com Version 1.0 – January 2010 1/12 Datasheet SHT21 Humidity and Temperature Sensor  Fully calibrated  Digital output, I2C interface  Low power consumption  Excellent long term stability  DFN type package – reflow solderable Dimensions Figure 1: Drawing of SHT21 sensor package, dimensions are given in mm (1mm = 0.039inch) , tolerances are ±0.1mm . Die pad (centre pad) is internally connected to VSS. NC are floating. VSS = GND, SDA = DATA. Sensor Chip SHT21 feature s 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. Material Contents While the sensor its elf 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. Additional Information and Evaluation Kits Additional information such as Application Notes is available from the web page www.sensirion.com/sht21. For more information please contact Sensirion via info@sensirion.com. For SHT21 tw o 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. 1.0 1.0 2.4 0.3 0.4 1.5 0.4 0.75 1.1 0.2 SCL SDA NC NC VSS VDD Bottom View SHT21 D0AC4 3.0 2.2 0.8 typ 1.4 typ 3.0 0.3 typ 2.0 typ Product Summary SHT21, the new humi dity 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 a n improved band gap temperature sensor the performance has been lifted even beyond the outstanding level of the previous sensor generati on (SHT1x and SHT7x). For example, measures have been taken to stabilize the behavior at high humidity levels. 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 miniaturizatio n 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.

www.sensirion.com Version 1.0 – January 2010 2/12 Sensor Performance Relative Humidity1234 Parameter Condition min typ max Units 12 bit 0.04 %RH Resolution 1 8 bit 0.7 %RH typ 2.0 %RH Accuracy tolerance 2 max see Figure 2 %RH Repeatability 0.1 %RH Hysteresis 1 %RH Nonlinearity <0.1 %RH Response time 3  63% 8 s Operating Range extended 4 0 100 %RH Long Term Drift 5 normal < 0.5 %RH/yr ± 0 ± 2 ± 4 ± 6 ± 8 ± 10 0 10 20 30 40 50 60 70 80 90 100 Relative Humidity (%RH) RH (%RH) maximal tolerance typical tolerance Figure 2 Typical and m aximal tolerance at 25°C for relative humidity. For extensive information see Users Guide, Sect. 1.2. 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 measuring 0.8 0.9 1.0 mW Power Dissipation 6 average 8bit - 1.5 - µW Heater VDD = 3.0 V 5.5mW, T = + 0.5-1.5°C Communication digital 2-wire interface, true I2C protocol Table 1 Electrical specification. For absolute maximum values see Chapter 3 of Users Guide. 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. 2 Accuracies are tested at Outgoing Quality Control at 25°C (77°F) and 3.0V . Values exclude hysteresis and non -linearity and are applicable to non - condensing environments only. 3 Time for achieving 63% of a step function, valid at 25°C and 1 m/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. Temperature567 Parameter Condition min typ max Units 14 bit 0.01 °C Resolution 1 12 bit 0.04 °C typ 0.3 °C Accuracy tolerance 2 max see Figure 3 °C Repeatability 0.1 °C -40 125 °C Operating Range extended 4 -40 257 °F Response Time 7  63% 5 30 s Long Term Drift < 0.04 °C/yr ± 0.0 ± 0.5 ± 1.0 ± 1.5 ± 2.0 ± 2.5 ± 3.0 -40 -20 0 20 40 60 80 100 120 Temperature (°C) T (°C) Figure 3 Maximal tolerance for temperature sensor in °C. Packaging Information Sensor Type Packaging Quantity Order Number Tape & Reel 400 1-100707-01 Tape & Reel 1500 1-100645-01 SHT21 Tape & Reel 5000 1-100694-01 This datasheet is subject to change and may be amended without prior notice.

5 Value may be higher in environments with vaporized solvents, out -gassing

tapes, adhesives, packaging materials, etc. For more details pl ease 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 senso r substrate.

1 Extended Specifications

1.1 Operating Range

may temporarily offset the RH signal (+3 %RH after 60h). exposure to extreme conditions may accelerate ageing.

1.2 RH accuracy at various temperatures

Figure 2. For other temperatures maximal tolerance has been evaluated to be within limits displayed in Figure 58. given in %RH for temperatures 0 – 80°C. half the maximal tolerance at other values.

8 Details on how Sensirion is specifying and testing accuracy performance are

planned to be published on the Sensirion web page.

2 Application Information

2.1 Soldering Instructions

of the sensor pads is plated with Ni/Pd/Au. outer dimension of the DFN package.

9 The land pattern is understood to be the metal layer on the PCB, onto which

the DFN pads are soldered to.

10 The solder mask is understood to be the insulating layer on top of the PCB

covering the connecting lines .

www.sensirion.com Version 1.0 – January 2010 4/12 the package. The die pad aperture should cover about 70 – 90% of the pad area – say up to 1.4mm x 2.3mm centered on the thermal land area. It c an also be split in two openings. Due to the low mounted height of the DFN, “no clean” type 3 solder paste11 is recommended as well as N itrogen purge during reflow. Figure 7 Soldering profile according to JEDEC standard. T P <= 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 7). For manual soldering contact time must be limited to 5 seconds at up to 350°C12. 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. 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 application s with exposure of the sensor to corrosive gases the soldering pads shall be sealed to prevent loose contacts or short cuts.

2.2 Storage Conditions and Handling Instructions

Moisture Sensitivity Level (MSL) is 2; hence storage time is limited to one year.

11 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). 12 260°C = 500°F, 350°C = 662°F It is of great importance to understand that a humi dity 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. For this reason 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 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 re commend to store them in ESD bags made of PE-HD13. 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 m aterial 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.

2.3 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: 100 – 105°C at < 5%RH for 10h Re-Hydration: 20 – 30°C at ~ 75%RH for 12h 14.

2.4 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 sen sor and test sensor must show equal temperature to allow for comparing humidity 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 8. Furthermore, there are self -heating effects in case the 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. 13 For example, 3M antistatic bag, product “1910” with zipper. 14 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 Temperature Time tP TP TL TS (max) tL preheating critical zone

www.sensirion.com Version 1.0 – January 2010 5/12 Figure 8 Top view of example of mounted SHT2x with slits milled into PCB to minimize heat transfer.

2.5 Light

The SHT2x is not light sensitive. Prolonged direct exposure to sunshine or strong UV radiation m ay age the sensor.

2.6 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), PEEK, PP, PB, PPS, PSU, PVDF, PVF. For sealing and gluing (use sparingly): Use high filled epoxy for electronic packaging (e.g. glob top, underfill), and Silicone. Out -gassing of these material s may also contaminate the sensor (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.

2.7 Wiring Considerations and Signal Integrity

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. Furt hermore, slowing down SCL frequency will possibly improve signal integrity. Power supply pins (VDD, VSS ) must be decoupled with a 100nF capacitor – see next Section.

3 Interface Specifications

2 VSS Ground

1 SDA Serial Data, bidirectional

6 SCL Serial Clock, bidirectional

5 VDD Supply Voltage

3,4 NC Not Connected, floating Table 2 SHT2x pin assignment, NC remain floating

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 9.

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 t SU and t HD before the rising and after the falling edge of SCL, respectively – see Figure 10. For reading data from the sensor, SDA is valid t VD after SCL has gone low and remains valid until the next falling edge of SCL. Figure 9 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. E xternal 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). I t should be noted that pull-up resistors may be incl uded in I/O circuits SDA SCL GND VDD MCU (master) RP RP SCL OUT SDA OUT SDA IN SCL IN C = 100nF SHT2x (slave) 1 6 5 2 4 3

characteristic of the sensor.

4 Electrical Characteristics

4.1 Absolute Maximum Ratings

Table 1. The absolute maximum ratings as given in Table 3 are stress ratings only and give additional information . reliability (e.g. hot carrier degradation, oxide breakdown).

4.2 Input / Output Characteristics

strictly within the limits given in Table 4 & 5 and Figure 10. 2.1 V to 3.6 V, T = -40 °C to 125 °C, unless otherwise noted. (SDA read and SDA write) refer to the left SCL toggle. 3.6V, T = -40°C to 125°C, unless otherwise noted.

5 Communication with Sensor

http://www.standardics.nxp.com/support/i2c/.

5.1 Start Up Sensor

15 For sensors with alternative I 2C address please contact Sensirion via

www.sensirion.com Version 1.0 – January 2010 7/12 commands from the master (MCU). Current consumption during start up is 350µA maximum.

5.2 Start / Stop Sequence

Each transmi ssion sequence begins with Start condition (S) and ends with Stop condition (P) as displayed in Figure 11 and Figure 12. Figure 11 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). Figure 12 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).

5.3 Sending a Command

After sending the Start condition, the subsequent I 2C 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 8 th 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 Comment Code Trigger T measurement hold master 1110’0011 Trigger RH measurement hold master 1110’0101 Trigger T measurement no hold master 1111’0011 Trigger RH measurement no hold master 1111’0101 Write user register 1110’0110 Read user register 1110’0111 Soft reset 1111’1110 Table 6 Basic command set, RH stands for relative humidity, and T stands for temperature

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 rema ins open for other communication while the sensor is processing the measurement. No hold master mode allows for processing other I 2C communication tasks on a bus while the sensor is measuring. A communication sequence of the two modes is displayed in Figure 13 and Figure 14, respectively. In the hold master mode , the SHT2x pulls down the SCL line while measuring to force the master into a wait s tate. By releasing the SCL line the sensor indicates that internal processing is terminat ed and that transmission may be continued. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 S 1 0 0 0 0 0 0 0 ACK 1 1 1 0 0 1 0 1 ACK I2C address + write Command (see Table 6) 19 20 21 22 23 24 25 26 27 S 1 0 0 0 0 0 0 1 ACK Measurement I2C address + read Hold during measurement 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 ACK 0 1 0 1 0 0 1 0 ACK Data (MSB) Data (LSB) Stat. 46 47 48 49 50 51 52 53 54 0 1 1 0 0 0 1 1 NACK P Checksum Figure 13 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 I 2C header (1000’0001) as shown in Figure 14. 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 LSBs (bits 43 and 44) are used for transmit ting status information. Bit 1 of the two LSBs indicates the measurement type (‘0’: temperature, ‘1’ humidity). Bit 0 is currently not assigned. SDA SCL 70% 30% 70% 30% SDA SCL 70% 30% 70% 30%

www.sensirion.com Version 1.0 – January 2010 8/12 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 S 1 0 0 0 0 0 0 0 ACK 1 1 1 1 0 1 0 1 ACK I2C address + write Command (see Table 6) 19 20 21 22 23 24 25 26 27 Measurement S 1 0 0 0 0 0 0 1 NACK measuring I2C address + read 19 20 21 22 23 24 25 26 27 Measurement S 1 0 0 0 0 0 0 1 ACK continue measuring 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 ACK 0 1 0 1 0 0 1 0 ACK Data (MSB) Data (LSB) Stat. 46 47 48 49 50 51 52 53 54 0 1 1 0 0 0 1 1 NACK P Checksum Figure 14 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. In the examples given in Figure 13 and Figure 14 the sensor output is S RH = ‘0110’0011’0101’0000’. For the calculation of physical values Status Bits must be set to ‘0’ – see Chapter 6. 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 T typ T max Units 14 bit 66 85 ms 13 bit 33 43 ms

12 Bit 22 29 17 22 ms

Table 7 Measurement time s for RH and T measurements at different resoluti ons. Typical values are recommended for calculating energy consumption while maximum values shall be applied for calculating waiting times in communication. Please note: I 2C communication allows for repeated Start conditions (S) without closing prior seque nce with Stop condition (P) – compare Figures 13, 14 and 16. Still, any sequence with adjacent Start condition may alternatively be closed with a Stop condition.

5.5 Soft Reset

This command (see Table 6) is used for re booting 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. The soft reset takes less than 15 ms. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 S 1 0 0 0 0 0 0 0 ACK 1 1 1 1 1 1 1 0 ACK P I2C address + write Soft Reset Figure 15 Soft Reset – grey blocks are controlled by SHT2x.

5.6 User Register

The content of user register is described in Table 8. Please note that reserved bits must not be changed. Bit # Bits Description / Coding Default 7, 0 2 Measurement resolution RH T ‘00’ 12 bit 14 bit ‘01’ 8 bit 12 bit ‘10’ 10 bit 13 bit ‘11’ 11 bit 11 bit ‘00’ 6 1 Status: End of battery16 ‘0’: VDD > 2.25 V ‘1’: VDD < 2.25 V ‘0’ 3, 4, 5 3 Reserved 2 1 Enable on-chip heater ‘0’ 1 1 Disable OTP reload ‘1’ 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. The End of B attery alert is activated when the battery power falls below 2.25V. The heater is intended to be used for funct ionality 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 before every me asurement. This feature is disabled per default and is not recommended for use. Please use Soft Reset instead – it contains OTP Reload. An example for I2C communication reading and writing the User Register is given in Figure 16. It is important that first the content of the register is read in order getting the default values. Hereafter, the resolution is changed by configuring register. Please note that the reserved user - register bits must not be changed.

16 This status bit is updated after each measurement

www.sensirion.com Version 1.0 – January 2010 9/12 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 S 1 0 0 0 0 0 0 0 ACK 1 1 1 0 0 1 1 1 ACK I2C address + write Read Register 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 S 1 0 0 0 0 0 0 1 ACK 0 0 0 0 0 0 1 0 NACK 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 ACK 1 1 1 0 0 1 1 0 ACK I2C address + write Write Register 55 56 57 58 59 60 61 62 63 0 0 0 0 0 0 1 1 ACK P Register content to be written Figure 16 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

For implementing CRC8 checksum please refer to Wikipedia (http://en.wikipedia.org/wiki/crc8).

5.8 Serial Number

SHT21 provides an e lectronic identification code. For instructions on how to r ead the identification code please refer to the Application Note “Electronic Identification Code” – to be downloade d from the web page www.sensirion.com/SHT21.

6 Conversion of Signal Output

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 13 and Figure 14, 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: RH S1256 RH  In the example given in Figure 13 and Figure 14 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 rela tive 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:  tλ tβ tλ tβRHRH i i w w wi expexp 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

7 Environmental Stability

The SHT2x sensor series were tested according to AEC - Q100 Rev. F qualification test method. Sensor specifications are tested to prevail under the AEC -Q100 temperature grade 2 test conditions listed in Table 917. Sensor performance under other test conditions cannot be guaranteed and i s not part of the sensor specifications. Especially, no guarantee can be given for sensor performance in the field or for customer’s specific application. Environment Standard Results18 HTSL 125°C, 1000 hours Within specifications TC -50°C - 125°C, 1000 cycles Acc. JESD22-A104-C Within specifications UHST 130°C / 85%RH, 96h Within specifications THU 85°C / 85%RH, 1000h Within specifications ESD immunity MIL STD 883E, method 3015 (Human Body Model at ±2kV) Qualified Latch-up force current of ±100mA with Tamb = 80°C, acc. JEDEC 17 Qualified Table 9: Qualification tests: HTSL = High Temperature Storage Lifetime, TC = Temperature Cycles, UHST = Unbiased Highly accelerated Stress Test, THU = Temperature Humidity Unbiased.

17 Sensor operation temperature range is -40 to 105°C according to AEC -Q100

temperature grade 2. 18 According to accuracy and long term drift specification given on Page 2.

www.sensirion.com Version 1.0 – January 2010 10/12 If s ensors 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 “Qualification Guide”.

8 Packaging

8.1 Packaging Type

SHT2x sensors are provided in DFN packaging ( in analogy with QFN packaging). DF N stands for Dual Flat No leads. The sensor chip is mounted to a lead frame m ade of Cu and pla ted 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 by February 2010. For testing of SHT2x sensors sockets , such as from Plastronics, part number 10LQ50S13030 are

8.3 Traceability Information

All SHT2 x are laser marked with an alphanumeri c, five - digit code on the sensor – see Figure 17. 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 t he 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 allo ws for tracking on batch level through production, calibration and testing – and will be provided upon justified request. Figure 17 Laser marking on SHT21. For details see text. Reels are also labeled, as displayed in Figure 18 and Figure 19, and give additional traceability information. Figure 18: First label on reel: XX = Sensor Type (21 for SHT21), O = Output mode (D = Digital, P = PWM, S = SDM), N N = Chip Version, Y = last digit of year, RRRR = number of sensors on reel, TTTT = Traceability Code. Figure 19: Second label on reel: For Device Type and Part 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.

8.4 Shipping Package

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, e ach 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 20. The reels are provided in sealed antistatic bags. Figure 20 Sketch of packaging tape and sensor orientation. Header tape is to the right and trailer tape to the left on this sketch. 8.0 2.0 4.00.3 1.3 R0.3 MAX R0.25 Ø0.15 MIN Ø0.15 MIN 3.3 0.25 3.3 1.75 5.5 12.0 SHT21 D0AC4 Device Type: 1-100PPP-NN Description: Humidity & Temperature Sensor SHTxx Part Order No. 1-100PPP-NN or Customer Number Date of Delivery: DD.MM.YYYY Order Code: 45CCCC / 0 Lot No.: XXO-NN-YRRRRTTTT Quantity: RRRR RoHS: Compliant Lot No.

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9 Compatibility to SHT1x / 7x protocol

SHT2x sensors may be run by communicating with the Sensirion specific communication protocol used for SHT1x and SHT7x. In case such protocol is ap plied 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 as well as the calculation of physical values in this SHT2x datasheet apply.

www.sensirion.com Version 1.0 – January 2010 12/12

Revision History

Date Version Page(s) Changes 6 May 2009 0.3 1 – 9 Initial preliminary release 7 Sept 2009 0.5 1,3,6,8-9 Revise Section 1.2, Figs. 1, 5 and 9, Table 5. Add Chapter 7 21 January 2010 1.0 1 – 4, 7 – Complete revision. For complete revision list please require respective document from Sensirion. 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. Befor e 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 o ut 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 inher ent 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 b e 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 © 2010, by SENSIRION. CMOSens® is a trademark of Sensirion All rights reserved Headquarter and Sales Offices Headquarter SENSIRION AG Phone: +41 44 306 40 00 Laubisruetistr. 50 Fax: +41 44 306 40 30 CH-8712 Staefa ZH info@sensirion.com Switzerland http://www.sensirion.com/ Sales Office USA: SENSIRION Inc. Phone: +1 805 409 4900 2801 Townsgate Rd., Suite 204 Fax: +1 805 435 0467 Westlake Village, CA 91361 michael.karst@sensirion.com USA http://www.sensirion.com/ Sales Office Japan: SENSIRION JAPAN Co. Ltd. Phone: +81 3 3444 4940 Postal Code: 108-0074 Fax: +81 3 3444 4939 Shinagawa Station Bldg. 7F, info@sensirion.co.jp 4-23-5, Takanawa, Minato -ku http://www.sensirion.co.jp Tokyo, Japan Sales Office Korea: SENSIRION KOREA Co. Ltd. Phone: +82 31 440 9925~27 #1414, Anyang Construction Tower B/D, Fax: +82 31 440 9927 1112-1, Bisan-dong, Anyang-city info@sensirion.co.kr Gyeonggi-Province http://www.sensirion.co.kr South Korea Sales Office China: Sensirion China Co. Ltd. phone: +86 755 8252 1501 Room 2411, Main Tower fax: +86 755 8252 1580 Jin Zhong Huan Business Building, info@sensirion.com.cn Futian District, Shenzhen, www.sensirion.com.cn Postal Code 518048 PR China Find your local representative at: http://www.sensirion.com/reps