www.sensirion.com Version 5 – October 2022 1/14
Datasheet SHT21
Humidity and Temperature Sensor IC
▪ Fully calibrated
▪ Digital output, I
2
C interface
▪ Low power consumption
▪ Excellent long-term stability
▪ DFN type package – reflow solderable
Dimensions
Figure 1: Drawing of SHT21 sensor package, dimensions are
given in mm (1 mm = 0.039 inch), tolerances are ±0.1 mm. The
die pad (center pad) is internally connected to VSS. The NC
pads must be left floating. VSS = GND, SDA = DATA.
Numbering of E/O pads starts at lower right corner (indicated by
notch in die pad) and goes clockwise (compare Table 2).
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.
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 SHT2x 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.
1.0
1.0
2.4
0.3
0.4
1.5
0.4
0.75
1.1
0.2
SCL
SDA
NC
NC
VSS
VDD
Bottom
View
SHT21
D0AC4
3.0
2.2
1.4 max
3.0
0.3 typ
2.4 max
Product Summary
The SHT21 humidity and temperature sensor of Sensirion
has become an industry standard in terms of form factor
and intelligence: Embedded in a reflow solderable Dual
Flat No leads (DFN) package of 3 x 3mm foot print and
1.1 mm height it provides calibrated, linearized sensor
signals in digital, I
2
C format.
The SHT2x sensors contain a capacitive type humidity
sensor, a band gap temperature sensor and specialized
analog and digital integrated circuit – all on a single
CMOSens
®
chip. This yields in an unmatched sensor
performance in terms of accuracy and stability as well as
minimal power consumption.
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
SHT2x can be changed by command (8/12 bit up to
12/14 bit for RH/T) and a checksum helps to improve
communication reliability.
With this set of features and the proven reliability and
long-term stability, the SHT2x sensors offer an
outstanding performance-to-price ratio. For testing SHT2x
two evaluation kits EK-H4 and EK-H5 are available.
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