Temperature Sensor IC
Digital output, I2C interface
Low power consumption
Excellent long term stability
DFN type package – reflow solderable
STS21, the new 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, I2C
Using the same CMOSens® technology as Sensirion‟s
successful and industry proven SHT2x humidity and
temperature sensors, the STS21 offers superior
performance and reliability. The ±0.2°C temperature
specification allows for implementation of the STS21 in
applications with high demands on temperature accuracy.
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
STS21 can be changed by command (11bit up to 14bit),
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.
STS21 features a generation 4C CMOSens® chip.
Besides the band gap temperature sensor, the chip
contains an amplifier, A/D converter, OTP memory and a
digital processing unit.
NC VDD SCL
NC VSS SDA
Figure 1 Drawing of STS21 sensor package, dimensions are
given in mm (1mm = 0.039inch), tolerances are ±0.1mm. 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).
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. For more
information please contact Sensirion via
For STS21 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.
Version 2 – December 2011