SHT25

Datasheet SHT25 Humidity and Temperature Sensor IC      Fully calibrated with 1.8%RH accuracy Digital output, I2C interface Low power consumption Excellent long term stability DFN type package – reflow solderable Product Summary The SHT25 high accuracy humidity and temperature sensor of Sensirion has become an industry standard in terms of form factor 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 sensor signals in digital, I2C format. The SHT2x sensors contain a capacitive type humidity sensor, a band gap temperature sensor and specialized analog and digital integrated circuit – all on a single CMOSens® chip. This yields in an unmatched sensor performance in terms of accuracy and stability as well as minimal power consumption. 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 SHT2x can be changed by command (8/12bit up to 12/14bit for RH/T) and a checksum helps to improve communication reliability. With this set of features and the proven reliability and long-term stability, the SHT2x sensors offer an outstanding performance-to-price ratio. For testing SHT2x two evaluation kits EK-H4 and EK-H5 are available. Sensor Chip 3.0 SHT25 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. 2.4 max 3.0 SHT21 D0AC4 0.3 typ 1.4 max 0.2 0.3 Bottom View NC VDD 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. SCL 0.75 0.4 Material Contents 1.1 2.2 0.4 1.5 2.4 1.0 Additional Information and Evaluation Kits 1.0 NC VSS SDA Figure 1: Drawing of SHT25 sensor package, dimensions are given in mm (1mm = 0.039inch), tolerances are ±0.1mm. The die pad (center pad) is internally connected to VSS. The NC pads must 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). www.sensirion.com Additional information such as Application Notes is available from the web page www.sensirion.com/sht25. For more information please contact Sensirion via info@sensirion.com. For SHT25 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. Version 3 – May 2014 1/14 Sensor Performance Relative Humidity Temperature Parameter Condition 12 bit 8 bit Value 0.04 0.7 Units %RH %RH typ 1.8 see Figure 2 %RH Repeatability 0.1 %RH Repeatability Hysteresis 1 80%RH). For more details please see Section 1.1 of the Users Guide. 5 Typical value for operation in normal RH/T operating range. Max. value is < 0.5 %RH/y . Value may be higher in environments with vaporized solvents, outgassing tapes, adhesives, packaging materials, etc. For more details please refer to Handling Instructions. www.sensirion.com typ 3.0 0.15 300 0.5 0.9 3.2 max Units 3.6 V 0.4 µA 330 µA 1.2 µW 1.0 mW µW 5.5mW, DT = + 0.5-1.5°C digital 2-wire interface, I2C protocol VDD = 3.0 V 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. 6 Response time depends on heat conductivity of sensor substrate. Max. value is < 0.04°C/y. 8 Min and max values of Supply Current and Power Dissipation are based on fixed VDD = 3.0V and T80%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. Prolonged exposure to extreme conditions may accelerate ageing. 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 100 80 0 60 Normal Range 40 Max. Range 0 20 40 60 80 100 120 Temperature (°C) Figure 4 Operating Conditions 1.2 RH accuracy at various temperatures Typical RH accuracy at 25°C is defined in Figure 2. For other temperatures, typical accuracy has been evaluated to be as displayed in Figure 5. 100 ±3 ±2.5 ±2.5 ±2.5 ±2.5 ±2.5 ±3 ±3.5 ±3.5 90 ±3 ±2.5 ±2 ±2 ±2 ±2 ±2.5 ±3 ±3.5 80 ±2.5 ±2 ±1.8 ±1.8 ±1.8 ±2 ±2 ±2.5 ±3 70 ±2.5 ±2 ±1.8 ±1.8 ±1.8 ±1.8 ±2 ±2 ±2.5 60 ±2 ±1.8 ±1.8 ±1.8 ±1.8 ±1.8 ±1.8 ±2 ±2 50 ±2 ±1.8 ±1.8 ±1.8 ±1.8 ±1.8 ±1.8 ±1.8 ±2 40 ±2 ±1.8 ±1.8 ±1.8 ±1.8 ±1.8 ±1.8 ±1.8 ±1.8 30 ±2 ±1.8 ±1.8 ±1.8 ±1.8 ±1.8 ±1.8 ±1.8 ±1.8 20 ±2 ±2 ±1.8 ±1.8 ±1.8 ±1.8 ±1.8 ±1.8 ±1.8 10 ±2.5 ±2.5 ±2 ±2 ±2 ±2 ±2 ±2 ±2 0 ±3 ±3 ±2.5 ±2.5 ±2.5 ±2.5 ±2.5 ±2.5 ±2.5 0 10 Supply Current IDD (nA) -20 40 60 80 100 120 Figure 6 Dependency of supply current (sleep mode) versus temperature at VDD = 3.0V. Please note the variance of the displayed data may exceed ±25%. 20 -40 20 Temperature (°C) 0 Relative Humidity [%RH] 8 7 6 5 4 3 2 1 0 20 18 16 14 12 10 8 6 2.1 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 the variance of the displayed data may exceed ±25%. 30 40 50 60 70 80 Temperature [°C] Figure 5 Typical accuracy of relative humidity measurements given in %RH for temperatures 0 – 80°C. www.sensirion.com 20 Version 3 – May 2014 3/14 Datasheet SHT25 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 lands9 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 mask10 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. 0.2 0.3 0.75 ≤1.4 1.5 ≤2.3 0.2 2.4 1.0 Due to the low mounted height of the DFN, “no clean” type 3 solder paste11 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 50°C for 24h to outgas contaminants before packing. 2.6 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. 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. 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. www.sensirion.com Version 3 – May 2014 5/14 Datasheet SHT25 3 Interface Specifications of MCUs. See Table 4 and Table 5 for detailed I/O characteristic of the sensor. Pin Name Comment 1 SDA Serial Data, bidirectional 4 2 VSS Ground 5 5 VDD Supply Voltage 6 SCL Serial Clock, bidirectional 6 3,4 NC Not Connected 3 2 1 Table 2 SHT2x pin assignment, NC must 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 SDA SHT2x (slave) 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 www.sensirion.com 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 conditions for extended periods may affect the sensor reliability (e.g. hot carrier degradation, oxide breakdown). 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 JESD22A114 method (Human Body Model at 4kV), JEDEC JESD22-A115 method (Machine Model 200V) and ESDA ESD-STM5.3.1-1999 and AEC-Q100-011 (Charged Device Model, 750V corner pins, 500V other pins). Latchup 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 The electrical characteristics such as power consumption, 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. Parameter RP SCL OUT SDA IN 4 Electrical Characteristics Conditions min typ max Units Output Low Voltage, VOL Output Sink Current, IOL Input Low Voltage, VIL Input High Voltage, VIH VDD = 3.0 V, -4 mA < IOL < 0mA 0 - 0.4 V - - -4 mA 0 - 30% VDD V 70% VDD - VDD V Input Current VDD = 3.6 V, VIN = 0 V to 3.6 V - - ±1 uA Table 4 DC characteristics of digital input/output pads. VDD = 2.1V to 3.6V, T = -40°C to 125°C, unless otherwise noted. Version 3 – May 2014 6/14 Datasheet SHT25 1/fSCL tSCLH tR tSCLL tF 70% SCL 30% tSU SDA valid write tHD DATA IN 70% SDA 30% SDA valid read tR tF tVD DATA OUT 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 min 0 0.6 1.3 100 0 0 0 0 0 typ - max 0.4 900 400 100 300 400 Units MHz µs µs ns ns ns ns ns 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. For further information regarding timing, please refer to http://www.standardics.nxp.com/support/i2c/. 5 Communication with Sensor SHT25 communicates with 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. Furthermore, please note, that Sensirion provides an exemplary sample code on its home page – compare www.sensirion.com/sht25. Please note that in case VDD is set to 0 V (GND), e.g. in case of a power off of the SHT2x, the SCL and SDA pads are also pulled to GND. Consequently, the I2C bus is blocked while VDD of the SHT2x is set to 0 V. www.sensirion.com 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 commands from the master (MCU). Current consumption during start up is 350µA maximum. Whenever the sensor is powered up, but not performing a measurement or communicating, it is automatically in idle state (sleep mode). 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. SCL SDA 70% 30% 70% 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). SCL SDA 70% 30% 70% 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). 5.3 Sending a Command 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. Version 3 – May 2014 7/14 Datasheet SHT25 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. 3 4 5 6 7 8 S 1 0 0 0 0 0 0 0 9 1 1 1 0 0 1 0 1 I2C address + write I2C ACK Measurement Hold during measurement ACK ACK 0 1 0 1 0 0 1 0 Data (MSB) 8 9 10 11 12 13 14 15 16 17 18 1 1 1 1 0 1 0 1 I2C address + write ACK 7 Command (see Table 6) wait P 20µs Measurement S 1 0 0 0 0 0 0 1 measuring NACK 19 20 21 22 23 24 25 26 27 P I2C address + read 19 20 21 22 23 24 25 26 27 Measurement S 1 0 0 0 0 0 0 1 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 0 1 0 1 0 0 1 0 Data (LSB) Stat. 46 47 48 49 50 51 52 53 54 P 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. 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 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 www.sensirion.com 6 Data (LSB) Stat. 46 47 48 49 50 51 52 53 54 0 1 1 0 0 1 0 0 5 Checksum 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 4 0 1 1 0 0 1 0 0 Command (see Table 6) address + read 3 S 1 0 0 0 0 0 0 0 19 20 21 22 23 24 25 26 27 S 1 0 0 0 0 0 0 1 2 Data (MSB) 10 11 12 13 14 15 16 17 18 ACK 2 ACK 1 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 Figure 15 and Figure 16, respectively. 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. ACK Table 6 Basic command set, RH stands for relative humidity, and T stands for temperature When using the no hold master mode it is recommended to include a wait period of 20 µs after the reception of the sensor’s ACK bit (bit 18 in Figure 16) and before the Stop condition. ACK Code 1110’0011 1110’0101 1111’0011 1111’0101 1110’0110 1110’0111 1111’1110 ACK Comment hold master hold master no hold master no hold master NACK Command Trigger T measurement Trigger RH measurement Trigger T measurement Trigger RH measurement Write user register Read user register Soft reset 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. 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. Version 3 – May 2014 8/14 Datasheet SHT25 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. 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. 3 4 5 6 7 8 S 1 0 0 0 0 0 0 0 I2C address + write 9 1 1 1 1 1 1 1 0 6 1 3, 4, 5 2 1 3 1 1 RH 12 bit 8 bit 10 bit 11 bit Status: End of battery14 ‘0’: VDD > 2.25V ‘1’: VDD < 2.25V Reserved Enable on-chip heater Disable OTP Reload 1 2 3 4 5 6 7 8 S 1 0 0 0 0 0 0 0 9 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, ‘0’ ‘1’ 1 1 1 0 0 1 1 1 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 The end of battery alert is activated when the battery power falls below 2.25V. ‘0’ 10 11 12 13 14 15 16 17 18 I2C address + write 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. T 14 bit 12 bit 13 bit 11 bit An example for I2C communication reading and writing the User Register is given in Figure 18. P Soft Reset Default ‘00’ 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. Figure 17 Soft Reset – grey blocks are controlled by SHT2x. www.sensirion.com Description / Coding Measurement resolution ‘00’ ‘01’ ‘10’ ‘11’ 10 11 12 13 14 15 16 17 18 ACK 2 ACK 1 # Bits 2 ACK 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. Bit 7, 0 0 0 0 0 0 0 1 0 I2C address + read NACK Units ms ms ms ms ms ms 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 ACK 29 15 9 4 T max 85 43 22 11 ACK 22 12 7 3 T typ 66 33 17 9 ACK RH max ACK RH typ Write Register 55 56 57 58 59 60 61 62 63 0 0 0 0 0 0 1 1 ACK Resolution 14 bit 13 bit 12 Bit 11 bit 10 bit 8 bit before every measurement. This feature is disabled per default and is not recommended for use. Please use Soft Reset instead – it contains OTP Reload. 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 SHT21 provides a CRC-8 checksum for error detection. The polynomial used is x8 + x5 + x4 +1. For more details and implementation please refer to the application note “CRC Checksum Calculation for SHT2x”. 14 This status bit is updated after each measurement Version 3 – May 2014 9/14 Datasheet SHT25 5.8 Serial Number SHT25 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/sht25. 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 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: 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  RHi  RHw  ex p w   λw  t   β t  ex p 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 7 Environmental Stability The SHT2x sensor series were tested based on AECQ100 Rev. G qualification test method where applicable. Sensor specifications are tested to prevail under the AECQ100 temperature grade 1 test conditions listed in Table 915. Environment Standard HTOL 125°C, 408 hours TC -50°C - 125°C, 1000 cycles Results16 Pass Pass UHST 130°C / 85%RH / ≈2.3bar, 96h Pass THB 85°C / 85%RH, 1000h Pass HTSL 150°C, 1000h Pass ELFR 125°C, 48h Pass ESD immunity HBM 4kV, MM 200V, CDM Pass 750V/500V (corner/other pins) Latch-up force current of ±100mA with Tamb Pass = 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, HTSL = High Temperature Storage Lifetime, ELFR = Early Life Failure Rate. For details on ESD see Sect. 4.1. 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 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 15 16 www.sensirion.com Packaging Type Temperature range is -40 to 125°C (AEC-Q100 temperature grade 1). According to accuracy and long term drift specification given on Page 2. Version 3 – May 2014 10/14 Datasheet SHT25 frame at diced edge is not covered with respective protective coating. The total weight of the sensor is 25mg. 8.3 Traceability Information 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 (SHT25). 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. 1-100PPP-NN Humidity & Temperature Sensor SHTxx Part Order No. 1-100PPP-NN or Customer Number Date of Delivery: DD.MM.YYYY Order Code: 46CCCC / 0 Figure 21: 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 and 1500 units per reel. For SHT25, 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 22. The reels are provided in sealed antistatic bags. 8.0 SHT25 D0AC4 2.0 4.0 0.3 Ø1.5 MIN Ø1.5 MIN 3.3 Reels are also labeled, as displayed in Figure 20 and Figure 21, and give additional traceability information. Lot No.: Quantity: RoHS: 5.5 R0.3 MAX Figure 19 Laser marking on SHT25. For details see text. XXO-NN-YRRRTTTTT RRRR Compliant 12.0 For testing of SHT2x sensors sockets, such as from Plastronics, part number 10LQ50S13030 are recommended (see e.g. www.locknest.com). Device Type: Description: 1.75 8.2 Filter Cap and Sockets For SHT2x a filter cap SF2 is available. It is designed for fast response times and compact size. Please find the datasheet on Sensirion’s web page. 1.3 3.3 0.25 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. Lot No. Figure 20: First label on reel: XX = Sensor Type (25 for SHT25), O = Output mode (D = Digital), NN = product revision no., Y = last digit of year, RRR = number of sensors on reel divided by 10 (200 for 2000 units), TTTTT = Traceability Code. 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 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 www.sensirion.com Version 3 – May 2014 11/14 Datasheet SHT25 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 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. www.sensirion.com Version 3 – May 2014 12/14 Datasheet SHT25 Revision History Date 11 June 2010 25 October 2010 December 2011 May 2014 www.sensirion.com Version 0.3 0.91 2 3 Page(s) 1–9 1 – 12 all 1-4, 7-8, 9-10 Changes Initial preliminary release Public release MSL and standards, minor text adaptations and corrections. Sensor window dimension updated, several minor adjustments Version 3 – May 2014 13/14 Datasheet SHT25  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 © 2014, by SENSIRION. CMOSens® is a trademark of Sensirion All rights reserved Headquarters and Subsidiaries SENSIRION AG Laubisruetistr. 50 CH-8712 Staefa ZH Switzerland Sensirion Inc., USA phone: +1 805 409 4900 info_us@sensirion.com www.sensirion.com Sensirion Korea Co. Ltd. phone: +82 31 337 7700~3 info@sensirion.co.kr www.sensirion.co.kr phone: +41 44 306 40 00 fax: +41 44 306 40 30 info@sensirion.com www.sensirion.com Sensirion Japan Co. Ltd. phone: +81 3 3444 4940 info@sensirion.co.jp www.sensirion.co.jp Sensirion China Co. Ltd. phone: +86 755 8252 1501 info@sensirion.com.cn www.sensirion.com.cn Sensirion AG (Germany) phone: +41 44 927 11 66 info@sensirion.com www.sensirion.com To find your local representative, please visit www.sensirion.com/contact www.sensirion.com Version 3 – May 2014 14/14