Datasheet SHT21
Humidity and Temperature Sensor
Fully calibrated
Digital output, I
2
C interface
Low power consumption
Excellent long term stability
DFN type package – reflow solderable
Product Summary
SHT21, the new humidity and temperature sensor of
Sensirion is about to set new standards in terms of size
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 signals in
digital, true I
2
C format.
With a completely new designed CMOSens® chip, a
reworked capacitive type humidity sensor and an
improved band gap temperature sensor the performance
has been lifted even beyond the outstanding level of the
previous sensor generation (SHT1x and SHT7x). For
example, measures have been taken to stabilize the
behavior at high humidity levels.
Dimensions
3.0
0.3 typ
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
SHT21 can be changed by command (8/12bit up to
12/14bit for RH/T), low battery can be detected and a
checksum helps to improve communication reliability.
With made improvements and the miniaturization of the
sensor the performance-to-price ratio has been improved
– and eventually, any device should benefit from the
cutting edge energy saving operation mode. For testing
SHT21 a new evaluation Kit EK-H4 is available.
Sensor Chip
SHT21 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.
1.1
0.2
SHT21
D0AC4
0.8 typ
2.0 typ
1.4
typ
3.0
2.2
Material Contents
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.
Additional Information and Evaluation Kits
Additional information such as Application Notes is
available from the web page
www.sensirion.com/sht21.
For more information please contact Sensirion via
info@sensirion.com.
For SHT21 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.
Bottom View
NC
VDD
SCL
0.4
0.75
0.3
0.4
1.5
2.4
1.0
1.0
NC
VSS
SDA
Figure 1:
Drawing of SHT21 sensor package, dimensions are
given in mm (1mm = 0.039inch), tolerances are ±0.1mm. Die
pad (centre pad) is internally connected to VSS. NC are floating.
VSS = GND, SDA = DATA.
www.sensirion.com
Version 1.0 – January 2010
1/12
SENSITRON [ SENSITRON ]
