Sensirion AG

World’s smallest digital humidity sensor: SHT21

With its new SHT21, Sensirion has presented the smallest digital humidity and tem-perature sensor to an intrigued audience in 2009. In the meantime the sensor has been characterized and qualified, and thousands of samples have been provided to interested users. The start of serial production is scheduled for April 2010.

The SHT21 consists of a newly designed, sophisticated sensor chip encapsulated in a DFN 3-0 package. With this encapsulation the chip is completely over-molded, ex-cept the humidity sensing area. In this way, the components size is reduced to a 3x3-mm footprint with 1.1-mm height. Additionally, over-molding provides excellent protec-tion against aging and ambient impact, such as condensation and harsh environ-ments, and thus yields outstanding long-term stability.

The fully calibrated state of the sensor and its true I2C digital interface ensure an easy application. Analog output modes (such as PWM) are available on request. The digi-tal communication mode enables superb low power consumption: A value in the range of 3μW at normal operation is well achieved and it may be lowered further by increasing the measurement interval. Typical sensor accuracy is ±2% RH over 20–80% RH and ±0.3 °C over 25–42 °C.

The SHT21 has been qualified in accordance with automotive standard AEC-Q100. Furthermore, an extended quality assur-ance program guarantees low PPM values. A scan path routine enables detailed sensor quality checking, while individual detailed tracking information on the chip can be read out by a simple command. Additionally, the SHT21 is reflow solderable without any degradation of sensor performance. The sensor is provided on tape & reel to enable standard, trouble-free han-dling. That all makes the SHT21 the perfect choice for high-volume applications.

Free samples of the SHT21 humidity and temperature sensor can be ordered at www.sensirion.com/mysht21.