SEK-SHT45-AD1B-SENSORS

SHT4x 4th Generation, High-Accuracy, Ultra-Low-Power, 16-bit Relative Humidity and Temperature Sensor Features • Relative humidity accuracy: up to ±1.0 %RH • Operating range: 0…100 %RH, -40…125 °C • Temperature accuracy: up to ±0.1 °C • Fully functional in condensing environment • Supply voltage: 1.08 V … 3.6 V • Variable power heater • Average current: 0.4 µA (at meas. rate 1 Hz) • NIST traceability • Idle current: 80 nA • JEDEC JESD47 qualification • I2C FM+, CRC checksum, multip. I2C addr. • Mature technology from global market leader • Patented on-package PTFE membrane [1] • Removable protection cap General Description SHT4x is a digital sensor platform for measuring relative humidity and temperature at different accuracy classes. Its I2C interface provides several preconfigured I2C addresses and maintains an ultra-low power budget. The power-trimmed internal heater can be used at three heating levels thus enabling sensor operation in demanding environments. The four-pin dual-flat-noleads package is suitable for surface mount technology (SMT) processing and comprises an optional on-package patented PTFE [1] membrane or a removable protection cap. Device Overview Products SHT40-AD1B SHT40-BD1B SHT40-AD1F SHT40-AD1P SHT41-AD1B SHT45-AD1B Functional Block Diagram Details base RH&T accur., 0x44 I2C addr. base RH&T accur., 0x45 I2C addr. add. patented on-package PTFE membrane add. removable protection cap Intermed. RH&T accur., 0x44 I2C addr. ±1.0 %RH, ±0.1°C accur., 0x44 I2C addr. Full product list on page 16 www.sensirion.com / D1 Version 3 – April 2022 1/18 Contents 1 Quick Start – Hello World ..................................................................................................................................... 3 2 Humidity and Temperature Sensor Specifications ....................................................................................... 4 2.1 Relative Humidity ............................................................................................................................................4 2.2 Temperature .....................................................................................................................................................6 2.3 Recommended Operating Conditions ......................................................................................................7 3 Electrical Specifications ........................................................................................................................................ 8 3.1 Electrical Characteristics ..............................................................................................................................8 3.2 Timings ...............................................................................................................................................................9 3.3 Absolute Maximum Ratings .........................................................................................................................9 4 Sensor Operation .................................................................................................................................................. 10 4.1 I2C communication.......................................................................................................................................10 4.2 I2C Communication Timing .......................................................................................................................10 4.3 Data type & length ........................................................................................................................................10 4.4 Checksum Calculation.................................................................................................................................10 4.5 Command Overview ....................................................................................................................................11 4.6 Conversion of Signal Output .....................................................................................................................11 4.7 Serial number .................................................................................................................................................12 4.8 Reset & Abort .................................................................................................................................................12 4.9 Heater Operation...........................................................................................................................................12 5 Physical Specification .......................................................................................................................................... 13 5.1 Package Description ....................................................................................................................................13 5.2 Package Outline ............................................................................................................................................13 5.3 Land Pattern ...................................................................................................................................................13 5.4 Pin Assignment & Laser Marking.............................................................................................................14 5.5 Thermal Information .....................................................................................................................................15 6 Quality and Material Contents........................................................................................................................... 15 7 Tape and Reel Packaging .................................................................................................................................. 15 8 Product Name Nomenclature ............................................................................................................................ 16 9 Ordering Information ............................................................................................................................................ 16 10 Bibliography.......................................................................................................................................................... 17 11 Revision History .................................................................................................................................................. 17 www.sensirion.com / D1 Version 3 – April 2022 2/18 1 Quick Start – Hello World A typical application circuit for SHT4x is shown on the left-hand side of Figure 1. After reaching the minimal supply voltage and allowing for the maximal power-up time of 1 ms the sensor is ready for I2C communication. The quickest way to measure humidity and temperature is pseudo-coded on the right-hand side of Figure 1. Together with the conversion formulae given in equations ( 1 ), ( 2 ), and ( 3 ), the digital signals can be translated into relative humidity and temperature readings. Typical application circuit Pseudo code i2c_write(i2c_addr=0x44, tx_bytes=[0xFD]) wait_seconds(0.01) rx_bytes = i2c_read(i2c_addr=0x44, number_of_bytes=6) t_ticks = rx_bytes[0] * 256 + rx_bytes[1] checksum_t = rx_bytes[2] rh_ticks = rx_bytes[3] * 256 + rx_bytes[4] checksum_rh = rx_bytes[5] t_degC = -45 + 175 * t_ticks/65535 rh_pRH = -6 + 125 * rh_ticks/65535 if (rh_pRH > 100): rh_pRH = 100 if (rh_pRH < 0): rh_pRH = 0 Figure 1: Typical application circuit (left) and pseudo code (right) for easy starting. For details on the signal cropping in the last four lines see section 4.6. Find code resources and embedded drivers on: https://github.com/Sensirion/embeddedsht/releases CAD files can be downloaded from SnapEDA: https://www.snapeda.com/search/?q=sht4%3F&search-type=parts www.sensirion.com / D1 Version 3 – April 2022 3/18 2 Humidity and Temperature Sensor Specifications Every SHT4x is individually tested and calibrated and is identifiable by its unique serial number (see section 4.7 for details on the serial number). For the calibration, Sensirion uses transfer standards, which are subject to a scheduled calibration procedure. The calibration of the reference, used for the calibration of the transfer standards, is NIST traceable through an ISO/IEC 17025 accredited laboratory. 2.1 Relative Humidity Parameter SHT40 RH accuracy1 Conditions typ. max. typ. SHT41 RH accuracy1 SHT45 RH accuracy1 Repeatability2, 3 Resolution4 Hysteresis range5 Specified Response time7 Long-term drift8 max. typ. max. high medium low At 25°C extended6 t63% typ. Value 1.8 see Figure 2 1.8 see Figure 3 1.0 see Figure 4 0.08 0.15 0.25 0.01 0.8 0 to 100 4 1.62 V: fast mode plus - - 340 pF VDD < 1.62V, Rpullup > 820 Ω VDD = 1.62V … 2.0V, Rpullup > 390 Ω VDD > 2.0V, Rpullup > 390 Ω - - VDD V - - Ω - - Ω - V - V - 0.2* VDD 0.2* VDD Capacitive bus load can be determined from Cb < trise /(0.8473*Rp). Rise times are trise = 300 ns for fast mode and trise = 120 ns for fast mode plus Table 3: Electrical specifications. www.sensirion.com / D1 Version 3 – April 2022 8/18 3.2 Timings Max. values are measured at -40°C and 1.08 V supply voltage (based on characterization). Parameter Symbol Conditions Min. Typ. Power-up time tPU After hard reset, VDD ≥ VPOR - 0.3 1 Soft reset time tSR After soft reset - - 1 - 1.3 1.6 - 3.7 4.5 - 6.9 8.3 Long pulse 0.9 1 1.1 s Short pulse 0.09 0.1 0.11 s tMEAS,l Measurement duration tMEAS,m tMEAS,h Heater-on duration Low repeatability Med. repeatability High repeatability Max. Units Comments Time between VDD reaching VPOR and ms sensor entering idle state Time between ACK of soft reset command and ms sensor entering idle state. Also valid for I2C general call reset. Including tPU: The three repeatability modes differ with ms respect to measurement duration, noise level and ms energy consumption ms tHeater After that time the heater is automatically switched off After that time the heater is automatically switched off Table 4 System timing specifications. 3.3 Absolute Maximum Ratings Stress levels beyond those listed in Table 5 may cause permanent damage or affect the reliability of the device. These are stress ratings only and functional operation of the device at these conditions is not guaranteed. Ratings are only tested each at a time. Parameter Max. voltage on any pin Operating temperature range Storage temperature range11 ESD HBM ESD CDM Latch up, JESD78 Class II, 125°C Rating VSS - 0.3 V … VDD + 0.3 V -40 °C … 125 °C -40 °C …150 °C 2 kV 500 V +-100 mA Table 5: Absolute maximum ratings. 11 The recommended storage temperature range is 10-50°C. Please consult the document “SHTxx Handling Instructions” for more information. www.sensirion.com / D1 Version 3 – April 2022 9/18 4 Sensor Operation 4.1 I2C communication I2C communication is based on NXP’s I2C-bus specification and user manual UM10204, Rev.6, 4 April 2014. Supported I2C modes are standard, fast mode, and fast mode plus. Data is transferred in multiples of 16-bit words and 8-bit checksum (cyclic redundancy check = CRC). All transfers must begin with a start condition (S) and terminate with a stop condition (P). To finish a read transfer, send not acknowledge (NACK) and stop condition (P). Addressing a specific slave device is done by sending its 7-bit I2C address followed by an eighth bit, denoting the communication direction: “zero” indicates transmission to the slave, i.e. “write”, a “one” indicates a “read” request. Schematics of the I2C transfer types are sketched in Error! Reference source not found.. The sensor does not support clock-stretching. In case the sensor receives a read header and is still busy with e.g. measurement or heating, it will return a NACK. Measurement data can only be received once and will be deleted from the sensor’s register after the first acknowledged I2C read header. Figure 11: I2C transfer types: First a write header is sent to the I2C slave, followed by a command, for example “measure RH&T with highest precision”. After the measurement is finished the read request directed to this I2C slave will be acknowledged and transmission of data will be started by the slave. 4.2 I2C Communication Timing All details on the timing are following the interface specification of NXP’s user manual UM10204, Rev.6, 4 April 2014. Please follow mandatory capacitor and resistor requirements given in Table 3. 4.3 Data type & length I2C bus operates with 8-bit data packages. Information from the sensor to the master has a checksum after every second 8-bit data package. Humidity and temperature data will always be transmitted in the following way: The first value is the temperature signal (2 * 8-bit data + 8-bit CRC), the second is the humidity signal (2 * 8-bit data + 8-bit CRC). 4.4 Checksum Calculation For read transfers each 16-bit data is followed by a checksum with the following properties Property Name Message Length Polynomial Initialization Value CRC-8 16-bit 0x31 (x8 + x5 + x4 +1) 0xFF Reflect Input/Output Final XOR Examples false/false 0x00 CRC(0xBEEF) = 0x92 Table 6 Data checksum properties. The master may abort a read transfer after the 16-bit data if it does not require a checksum. www.sensirion.com / D1 Version 3 – April 2022 10/18 4.5 Command Overview Command (hex) Response length incl. CRC (bytes) Description [return values] 0xFD 6 0xF6 6 0xE0 6 0x89 6 0x94 - 0x39 6 0x32 6 0x2F 6 0x24 6 0x1E 6 0x15 6 measure T & RH with high precision (high repeatability) [2 * 8-bit T-data; 8-bit CRC; 2 * 8-bit RH-data; 8-bit CRC] measure T & RH with medium precision (medium repeatability) [2 * 8-bit T-data; 8-bit CRC; 2 * 8-bit RH-data; 8-bit CRC] measure T & RH with lowest precision (low repeatability) [2 * 8-bit T-data; 8-bit CRC; 2 * 8-bit RH-data; 8-bit CRC] read serial number [2 * 8-bit data; 8-bit CRC; 2 * 8-bit data; 8-bit CRC] soft reset [ACK] activate heater with 200mW for 1s, including a high precision measurement just before deactivation [2 * 8-bit T-data; 8-bit CRC; 2 * 8-bit RH-data; 8-bit CRC] activate heater with 200mW for 0.1s including a high precision measurement just before deactivation [2 * 8-bit T-data; 8-bit CRC; 2 * 8-bit RH-data; 8-bit CRC] activate heater with 110mW for 1s including a high precision measurement just before deactivation [2 * 8-bit T-data; 8-bit CRC; 2 * 8-bit RH-data; 8-bit CRC] activate heater with 110mW for 0.1s including a high precision measurement just before deactivation [2 * 8-bit T-data; 8-bit CRC; 2 * 8-bit RH-data; 8-bit CRC] activate heater with 20mW for 1s including a high precision measurement just before deactivation [2 * 8-bit T-data; 8-bit CRC; 2 * 8-bit RH-data; 8-bit CRC] activate heater with 20mW for 0.1s including a high precision measurement just before deactivation [2 * 8-bit T-data; 8-bit CRC; 2 * 8-bit RH-data; 8-bit CRC] Table 7 Overview of I2C commands. If the sensor is not ready to process a command, e.g. because it is still measuring, it will response with NACK to the I2C read header. Given heater power values are typical and valid for VDD=3.3V. 4.6 Conversion of Signal Output The digital sensor signals correspond to following humidity and temperature values: 𝑆𝑅𝐻 𝑅𝐻 = (−6 + 125 ∙ 16 ) %RH 2 −1 𝑆𝑇 𝑇 = (−45 + 175 ∙ 16 ) °C 2 −1 𝑆𝑇 𝑇 = (−49 + 315 ∙ 16 ) °F 2 −1 (1) (2) (3) N.B.: The RH conversion formula (1) allows values to be reported which are outside of the range of 0 %RH … 100 %RH. Relative humidity values which are smaller than 0 %RH and larger than 100 %RH are non-physical, however these “uncropped” values might be found beneficial in some cases (e.g. when the distribution of the sensors at the measurement boundaries are of interest). For all users who do not want to engage in evaluation of these non-physical values, cropping of the RH signal to the range of 0 %RH … 100 %RH is advised. www.sensirion.com / D1 Version 3 – April 2022 11/18 4.7 Serial number Each sensor has a unique serial number, that is assigned by Sensirion during production. It is stored in the one-time-programmable memory and cannot be manipulated after production. The serial number is accessible via I2C command 0x89 and is transmitted as two 16-bit words, each followed by an 8-bit CRC. 4.8 Reset & Abort A reset of the sensor can be achieved in three ways: • Soft reset: send the reset command described in Table 7. • I2C general call reset: all devices on I2C bus are reset by sending the command 0x06 to the I2C address 0x00. • Power down (incl. pulling SCL and SDA low) Any command that triggers an action at the sensor can be aborted via I2C general call reset or soft reset. 4.9 Heater Operation The sensor incorporates an integrated on-package heater which can be switched on by the set of commands given in Table 7. Three heating powers and two heating durations are selectable. After reception of a heater-on command, the sensor executes the following procedure: 1. The heater is enabled, and the timer starts its count-down. 2. On timer expiration a temperature and humidity measurement with the highest repeatability is started, the heater remains enabled. 3. After the measurement is finished the heater is turned off. 4. Temperature and humidity values are now available for readout. The maximum on-time of the heater commands is 1 second in order to prevent overheating of the sensor by unintended usage of the heater. Thus, there is no dedicated command to turn off the heater. For extended heating periods it is required to send periodic heater-on commands, keeping in mind that the heater is designed for a maximal duty cycle of less than 10%. To obtain a fast increase in temperature the idle time between consecutive heating pulses shall be kept minimal. Possible Heater Use Cases There will be dedicated Sensirion application notes elaborating on various use cases of the heater. In general, the applications of the on-package heater range around: 1. Removal of condensed / spray water on the sensor surface. Although condensed water is not a reliability / quality problem to the sensor, it will however make the sensor nonresponsive to RH changes in the air as long as there is liquid water on the surface. 2. Creep-free operation in high humid environments. Periodic heating pulses allow for creepfree high-humidity measurements for extended times. Important notes for operating the heater: 1. The heater is designed for a maximum duty cycle of 10%, meaning the total heater-on-time should not be longer than 10% of the sensor’s lifetime. 2. During operation of the heater, sensor specifications are not valid. 3. The temperature sensor can additionally be affected by the thermally induced mechanical stress, offsetting the temperature reading from the actual temperature. 4. The sensor’s temperature (base temperature + temperature increase from heater) must not exceed Tmax = 125 °C in order to have proper electrical functionality of the chip. 5. The heater draws a large amount of current once enabled (up to ~75mA in the highest power setting). Although a dedicated circuitry draws this current smoothly, the power supply must be strong enough to avoid large voltage drops that could provoke a sensor reset. www.sensirion.com / D1 Version 3 – April 2022 12/18 6. If higher heating temperatures are desired, consecutive heating commands have to be sent to the sensor. The heater shall only be operated in ambient temperatures below 65°C else it could drive the sensor outside of its maximal operating temperature. 5 Physical Specification 5.1 Package Description SHT4x is provided in an open-cavity dual flat no lead (DFN) package. The humidity sensor opening is centered on the top side of the package. The sensor chip is made of silicon, hosted on a copper lead frame and overmolded by an epoxy-based mold compound. Exposed bottom side of the leadframe with the metallic contacts is Ni/Pd/Au coated, side walls are bare copper. Moisture sensitivity level (MSL) of 1 according to IPC/JEDEC J-STD-020 is achieved. It is recommended to process the sensors within one year after date of delivery. 5.2 Package Outline Figure 12 Dimensional drawing of SHT4x including package tolerances (units mm). 5.3 Land Pattern The land pattern is recommended to be designed according to the used PCB and soldering process together with the physical outer dimensions of the sensor. For reference, the land pattern used with Sensirion’s PCBs and soldering processes is given in Figure 13. Soldering of the central die pad is optional. Sensirion recommends to not solder the central die pad because the sensor can reach higher temperatures upon heater activation. www.sensirion.com / D1 Version 3 – April 2022 13/18 Figure 13: Recommended land pattern (in mm). Details can vary and depend on used PCBs and solder processes. There shall be no copper under the sensor other than at the pin pads. 5.4 Pin Assignment & Laser Marking Pin 1 2 3 4 Name SDA SCL VDD VSS Comments Serial data, bidirectional Serial clock, unidirectional input Supply voltage Ground Figure 14 Pin assignment (transparent top view). Dashed lines are only visible if sensor is viewed from below. The die pad is not directly connected to any pin. The laser marking consists of two lines, indicated in Figure 14. In the first line a filled circle serves as pin-1 indicator and is followed by “SH4”. The last character will indicate the accuracy class of this product (here “x” serves as place holder). In the second line, the first three characters specify the product characteristics according to positions 7, 8 and 9 of Table 9. The second three characters serve as internal batch tracking code. www.sensirion.com / D1 Version 3 – April 2022 14/18 5.5 Thermal Information Symbol Description 𝑅𝜃𝐽𝐴 Junction-to-ambient thermal resistance Junction-to-case thermal resistance Junction-to-board thermal resistance Junction-to-board characterization param. Junction-to-top characterization param. 𝑅𝜃𝐽𝐶 𝑅𝜃𝐽𝐵 Ψ𝐽𝐵 Ψ𝐽𝑇 Heater off, die pad soldered (K/W) Heater on, die pad soldered (K/W) Heater off, die pad not soldered (K/W) Heater on, die pad not soldered (K/W) 246 308 297 357 189 255 191 257 159 225 193 258 159 223 191 254 38 105 44 112 Table 8 Typical values for thermal metrics. In the “heater on” columns a heater power of 200 mW was assumed. Soldering of the die pad is not recommended, therefore the two right hand side columns are bold. Values are based on simulation. 6 Quality and Material Contents Qualification of SHT4x is performed based on the JEDEC JESD47 qualification test method, qualification report available on request. The device is fully RoHS and WEEE compliant, e.g. free of Pb, Cd, and Hg. For general remarks of best practice in processing humidity sensor please refer to the handling instructions [2]. 7 Tape and Reel Packaging All specifications for the tape and reel packaging can be found on Figure 15. Reel diameters are 13 inch and 8 inch for the 10k and the 2.5k packaging sizes, respectively. Figure 15: Tape and reel specifications including sensor orientation in pocket (see indication of two sensors on the right side of the tape). www.sensirion.com / D1 Version 3 – April 2022 15/18 8 Product Name Nomenclature position 1 2 3 4 5 6 7 8 9 10 11 12 13 value(s) S H T 4 0 1 5 A B D 1 B F P R 2 3 explanation Sensirion Humidity Signal Temperature Signal Fourth product generation Base accuracy Intermediate accuracy Best accuracy delimiter I2C interface with 0x44 address I2C interface with 0x45 address DFN package reserved package without membrane Package with integrated, patented PTFE membrane Package with integrated, removable protection cap delimiter Tape on reel packaging Packaging article contains 2’500 pieces Packaging article contains 10’000 pieces Table 9 SHT4x product name nomenclature. 9 Ordering Information Material Description SHT40-AD1B-R2 SHT40-AD1B-R3 Material Number 3.000.465 3.000.353 SHT40-AD1F-R3 tbd SHT40-AD1P-R3 tbd SHT40-BD1B-R2 SHT40-BD1B-R3 SHT41-AD1B-R2 SHT41-AD1B-R3 SHT45-AD1B-R2 SHT45-AD1B-R3 3.000.492 3.000.610 3.000.466 3.000.611 3.000.645 3.000.750 Details base RH&T acc., 0x44 I2C addr. base RH&T acc., 0x44 I2C addr. base RH&T acc., 0x44 I2C addr., including patented PTFE membrane available Q3/22 base RH&T acc., 0x44 I2C addr., removable protection cap available Q3/22 base RH&T acc., 0x45 I2C addr. base RH&T acc., 0x45 I2C addr. intermed. RH&T acc., 0x44 I2C addr. intermed. RH&T acc., 0x44 I2C addr. ±1.0 %RH, ±0.1°C acc., 0x44 I2C addr. ±1.0 %RH, ±0.1°C acc., 0x44 I2C addr. Quantity (pcs) 2’500 10’000 10’000 10’000 2’500 10’000 2’500 10’000 2’500 10’000 Table 10 SHT4x ordering options. www.sensirion.com / D1 Version 3 – April 2022 16/18 10 Bibliography [1] K. Ehrhorn, "A Humidity Sensor and a Methode for Manufacturing the Same.". UK, DE, FR, NL, DM, BE, US, CN Patent EP1810013, US7741950, CN101040181, 2005. [2] Sensirion, "Handling Instructions for Humidity Sensors," 2020. 11 Revision History Date October 2020 July 2021 Version 1 2 April 2022 3 www.sensirion.com / D1 Page(s) all multiple 3 4 4 10 9 12 15 11 12 12 16 multiple multiple 4 4 4 9 10 16 16 Changes Initial release Typo correction Included checksum in Figure 1 Included description of NIST traceability in section 2 Included repeatability clarification in Table 1 Clarified I2C communication in section 4.1 Removed waiting time specification in Table 4 Specified serial number in 4.7 Updated qualification status in section 6 Deleted binary com. & included return values in Table 7 Updated note on duty cycle of heater in section 4.9 Added note on large current drawn by heater in section 4.9 Updated ordering information in Table 10 Included SHT45 RH- and T-accuracy specifications Extended max. heater duty cycle to 10% Reduced RH response time to 4s in Table 1 Reduced long-term drift to