Datasheet Humidity and Temeperature Sensor SHT21
14Pages

S6NSIRION TM StNSOR COMPANY Datasheet SHT21 Humidity and Temp)rature Sensor IC ■ Fully calibrated ■ Digital output, PC interface ■ Low power consumption ■ Excellent long term stability ■ DFN type package - reflow solderable Product Summary SHT21, the new humidrty and temprature sensor of Sensirion is about to set new standards m terms of size and Intelligence: Embedded in a reflow solderable Dual Fiat No leads (DFN) package of 3 x 3mm foot print and 1.1mm height rt provides calibrated, linearized signais in digital, \2Cformat. With a completely new designed CMOSens® chip, a reworked capacitive type humidity sensor and an improved band gap temprature sensor the performance has been lifted even beyond the outstanding level of the previous sensor g驩nration (SHT1x and SHT7x). For example, measures have been taken to stabilize the behavior at high humidity levete. Every sensor is individually calibrated and tested. Lot identification is pnnted 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 (8/12brt up to 12/14bit for RH/T), low battery can be detected and a checksum helps to improve communication reliability. Wrth made improvements and the miniatuhzation of the sensor the performance-to-price ratio has been improved - and eventually, any device should beneftt from the cutting edge energy saving opration mode. For testing SHT21 a new 驩valuation Kit EK-H4 is available. Dimensions Sensor Chip SHT21 features a generabon 4C CMOSens® chip. Besides the capacitive relative humidity sensor and the band gap temprature sensor, the chip contains an amplifier, A/D converter, OTP memory and a digital processing unit ^ ^ Material Contents While Pie sensor itself is made of Silicon the sensors1 housing consists of a plated Cu lead-frame and green epoxy-based moid compound. The device is fully RoHS and WEEE compilant, e.g. free of Pb, Cd and Hg. Brttom View nc voo sa Additional Information and Evaluation Kits Additional information such as Application Notes is available from the web page www.sensinon.com/5ht21. For more information please contact Sensinon via info@sensinonxom. For SHT21 two Evaluation Kits are available: EK-H4, a four-channel device wrth Viewer Software, that also serves for data-logging, and a simple EK-H5 directly Connecting one sensor via USB port lo a computer n n n Figure 1: Drawing ot SHT21 sensor package, imensions are given m mm (1mm = 0 039inch), loterances are ±0 1mm The *c pad (ccnter pad) is intcrnaly conneded to VSS The NC pads must be lefl floating VSS = GND. SDA = DATA Numbenng of E/O pads slarts at lower nghl corner (ndicated by notch in die pad) and goes ciockwtse (compare Table 2) www sensinufi.com Version 3 -Uecenber 2011 1/14

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Datasheet SHT21 S6N5IRION TH 5CNSOR COMPANY 2 Application Information 2-1 Soldering Instructions The DFN's die pad (centre pad) and penmeter I/O pads are (abricated from a planar copper lead-frame by over-molding leaving the die pad and I/O pads exposed for mechanical and electncal connection. Both the I/O pads and die pad should be soldered to the PCB. In order to prevent oxidabon and optimize soldering, the bottom side of the sensor pads is plated with Ni/Pd/Au. On the PCB the I/O lands? should be 0.2mm longer than the package I/O pads. Inward corners may be rounded to match the I/O pad...

Datasheet SH121 SENSIRION TH 5CNSOR COMPANY recommended to further process the sensors wrthin 1 year after dateof dekvery. tt is of great importance to understand that a humidity sensor is not a normal electronic component and needs to be handled with care, Chemical vapors at high concentrabon in combination with long exposure times may offset the sensor reading. For this reason it b recommended to store the sensors in onginal packaging induding the sealed ESD bag at following conditions: Temp)rature shall be in the range of 10*C - 50°C and humidity at 20 - 60%RH (sensors that are not...

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