SHTW1 Digital WLCSP Humidity & Temperature Sensor
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Data Sheet SHTW1 WLCSP Humidity and Temperature Sensor IC Ultra-small WLCSP: 1.3 × 0.7 × 0.5 mm3 Fully calibrated and reflow solderable Ultra-low power consumption Power-up and measurement within 1 ms 1.8 V supply voltage Typical accuracy: ±3 %RH and ±0.4 °C Product Summary The SHTW1 is a digital humidity and temperature sensor in a wafer-level chip-scale package (WLCSP). This type of package opens up a new category of ultra-small humidity sensors which are suitable for applications with the tightest space constraints. The SHTW1 is designed especially for high-volume consumer electronics applications. The sensor is based on Sensirion’s CMOSens® technology, which offers a complete sensor system on a single chip, consisting of a capacitive humidity sensor, a bandgap temperature sensor, analog and digital signal processing, A/D converter, calibration data memory, and a digital communication interface supporting I2C fast mode. Block diagram Benefits of Sensirion’s CMOSens® Technology The sensor covers a humidity measurement range of 0 to 100 %RH and a temperature measurement range of -30 to 100 °C with a typical accuracy of ±3 %RH and ±0.4°C. The operation voltage of 1.8 V and the low power consumption make the SHTW1 suitable for mobile or wireless applications running on the tightest power budgets. With the industry-proven quality and reliability of Sensirion’s humidity and temperature sensors and constant accuracy over a large measurement range, the SHTW1 offers an unprecedented performance-to-price ratio. Tape and reel packaging together with suitability for standard SMD assembly processes make the SHTW1 predestined for high-volume applications. High reliability and long-term stability Industry-proven technology with a track record of more than 10 years Designed for mass production Optimized for lowest cost Best signal-to-noise ratio Signal conditioning Signal conditioning Data processing and system control Calibration mem. VDD Figure 1 Functional block diagram of the SHTW1.

Humidity and Temperature Sensor Specifications Relative Humidity Table 2 Temperature sensor specifications. Table 1 Humidity sensor specifications. Maximal tolerance Maximal tolerance Typical tolerance Typical tolerance Figure 2 Typical and maximal tolerance for the relative humidity in %RH at 25 °C. Figure 3 Typical and maximal tolerance for the temperature sensor in °C. For definition of typ. and max. accuracy tolerance, please refer to the document “Sensirion Humidity Sensor Specification Statement”. 2 The stated repeatability is 3 times the standard deviation (3σ) of multiple...

1.1 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 4. ±4.5 ±4.5 ±4 ±4 ±3.5 ±3.5 ±3.5 ±3.5 ±3.5 ±4 ±4.5 The sensor shows best performance when operated within recommended normal temperature and humidity range of 5 – 60 °C and 20 – 80 %RH, respectively. Long term exposure to conditions outside normal range, especially at high humidity, may temporarily offset the RH signal (e.g. +3%RH after 60h at >80%RH). After returning into the normal temperature and humidity...

Parameter Supply voltage, VDD Operating temperature range Storage temperature range11 ESD HBM ESD MM ESD CDM Latch up, JESD78 Class II Table 4 Absolute maximum ratings. Timing Specifications 3.1 Sensor System Timings Default conditions of 25 °C and 1.8 V supply voltage apply to values the table below, unless otherwise stated. Max. values are measured at -30°C and 1.98V supply voltage. Parameter Power-up time After hard reset, VDD ≥ VPOR Soft reset time After soft reset. Measurement duration Units Comments Time between VDD reaching VPU µs and sensor entering idle state Time between ACK of...

Figure 5 Timing diagram for digital input/output pads. SDA directions are seen from the sensor. Bold SDA lines are controlled by the sensor, plain SDA lines are controlled by the micro-controller. Note that SDA valid read time is triggered by falling edge of preceding toggle. Pins 2 and 5 are not functional and should be left floating. Interface Specifications The SHTW1 supports I2C fast mode (SCL clock frequency from 0 to 400 kHz) with clock stretching. For detailed information on the I2C protocol, refer to NXP I2C-bus specification and user manual UM10204, Rev. 4, February 13, 2012:...

All commands and memory locations of the SHTW1 are mapped to a 16-bit address space which can be accessed via the I2C protocol. SHTW1 Table 8 SHTW1 I2C device address. 5.1 Power-Up and Communication Start Upon VDD reaching the power-up voltage level VPOR, the SHTW1 enters idle state after a duration of tPU. In idle state, the SHTW1 is ready to receive commands from the master (microcontroller). Each transmission sequence begins with START condition (S) and ends with an (optional) STOP condition (P) as described in the I2C-bus specification. Whenever the sensor is powered up, but not...

be sent to SHTW1 according to Figure 8. This triggers the sensor to reset all internal state machines and reload calibration data from the memory. Command Software reset 5.9 Conversion of Signal Output Measurement data is always transferred as 16-bit values. These values are already linearized and temperature compensated by the SHTW1. Humidity and temperature values can be calculated with the formulas in given below. Relative humidity conversion formula (result in %RH): S RH 100 RH 2 16 Table 10 Soft reset command. 5.7 Read-out of ID Register The SHTW1 has an ID register which contains an...

clock stretching disabled repeated I2C address + read while meas. is in prog. (polling) measurement cont’d measurement completed 5.10 Communication Data Sequences clock stretching enabled I2C address + read while meas. is in progress SHTW1 measuring, SCL line pulled low measurement continued Figure 7 Communication sequence for starting a measurement and reading measurement results displaying both clock stretching options. The numerical example corresponds to a read humidity-first command with clock stretching enabled. The physical values of the transmitted measurement results are 65.6 %RH...