SHT21S SENSIRION, SHT21S Datasheet

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SHT21S

Manufacturer Part Number
SHT21S
Description
SENSOR, HUMIDITY & TEMP
Manufacturer
SENSIRION
Datasheets

Specifications of SHT21S

Humidity Range
0 - 100% RH
Sensor Output
SDM - Convertible To Analogue
Sensor Terminals
SMD
Response Time
8s
Supply Voltage Range
2.1V To 3.6V
Accuracy
2% RH
Supply Voltage
3VDC
Rohs Compliant
Yes
Capacitance
0µF
Sensing Accuracy
2%
Operating Temperature Range
-40°C To +125°C
Msl
MSL 2 - 1 Year
Datasheet SHT21S
Humidity and Temperature Sensor
 Fully calibrated
 SDM interface convertible to analog output
 Low power consumption
 Excellent long term stability
 DFN type package – reflow solderable
Dimensions
Figure 1: Drawing of SHT21S sensor package, dimensions
are given in mm (1mm = 0.039inch), tolerances are ±0.1mm.
NC and die pad (center pad) are internally connected to VSS.
They may be left floating. Numbering of E/O pads starts at lower
right corner (indicated by notch in die pad) and goes clockwise
(compare Table 2).
www.sensirion.com
Product Summary
SHT21S, 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
analog Sigma Delta Modulated (SDM) format.
With a completely new designed CMOSens® chip, a
reworked capacitive type humidity sensor and an
improved band gap temperature sensor the performance
level has been lifted even beyond the outstanding
reliability level of the previous sensor generation (SHT1x
and SHT7x). For example, measures have been taken to
stabilize the behavior at high humidity levels.
1.0
0.4
3.0
2.4
2.2
0.8 typ
1.0
0.3 typ
0.3
Bottom View
NC
NC
1.1
VDD
VSS
Version 1.1 – May 2010
SCL
SDA
Sensor Chip
SHT21S feature 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 free of Pb, Cd
and Hg – hence it is fully RoHS and WEEE compliant.
Additional Information
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.
SDM signal is a pulse sequence that with a low pass filter
may be converted into analog voltage output. The data
signal is provided on SDA line. Pulling SCL high or low
allows for switching between humidity and temperature,
respectively. The sensor measures the physical values
twice per second.
Every sensor is individually calibrated and tested. Lot
identification is printed on the sensor.
With made improvements and the miniaturization of the
sensor the performance-to-price ratio has been improved.
SHT21 is also available with digital I
2
C or PWM interface.
1/9

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SHT21S Summary of contents

Page 1

... Figure 1: Drawing of SHT21S sensor package, dimensions are given in mm (1mm = 0.039inch), tolerances are ±0.1mm. NC and die pad (center pad) are internally connected to VSS. They may be left floating. Numbering of E/O pads starts at lower right corner (indicated by notch in die pad) and goes clockwise (compare Table 2) ...

Page 2

... Relative Humidity (%RH) Figure 3 Maximal temperature accuracy tolerance. For elec- tronic impacts on accuracy please consult Sect. 5.3. Packaging Information Sensor Type typ max Units 3.0 3.6 V SHT21S 160 µA 0. This datasheet is subject to change and may be amended without prior notice. 4 Value may be higher in environments with vaporized solvents, out-gassing tapes, adhesives, packaging materials, etc ...

Page 3

... Users Guide SHT21S 1 Extended Specifications For details on how Sensirion is specifying and testing accuracy performance please consult Application Note “Statement on Sensor Specification”. 1.1 Operating Range The sensor works stable within recommended Normal Range – see Figure 4. Long term exposure to conditions outside Normal Range, especially at humidity >80%RH, may temporarily offset the RH signal (+3%RH after 60h) ...

Page 4

... Datasheet SHT21S For solder paste printing a laser-cut, stainless steel stencil with electro-polished trapezoidal walls and with 0.125mm stencil thickness is recommended. For the I/O pads the stencil apertures should be 0.1mm longer than PCB pads and positioned with 0.1mm offset away from the centre of the package. The die pad aperture should cover about 70 – ...

Page 5

... Table 2 SHT21S pin assignment (top view) 3.1 Power Pins (VDD, VSS) The supply voltage of SHT21S must be in the range of 2.1 – 3.6V, recommended supply voltage is 3.0V. Power supply pins Supply Voltage (VDD) and Ground (VSS) must be decoupled with a 100nF capacitor, that shall be placed as close to the sensor as possible – ...

Page 6

... Datasheet SHT21S Parameter min VDD to VSS -0.3 Digital I/O Pins (SDA, SCL) -0.3 to VSS Input Current on any Pin -100 Table 3 Electrical absolute maximum ratings ESD immunity is qualified according to JEDEC JESD22- A114E method (Human Body Model at 4kV), JEDEC JESD22-A115A method (Machine Model 200V) and ESDA ESD-STM5 ...

Page 7

... Datasheet SHT21S 6 Conversion of Signal Output After the low pass filter the sensor provides an output Voltage V which as a portion of VDD then is converted SO into a physical value. Resolution is set to 10 bit for relative humidity and 12 bit for temperature and cannot be changed. The sensor reading is linearized and hence it can be converted to a physical value by an easy linear equation ...

Page 8

... Shipping Package SHT2x are provided in tape & reel shipment packaging, sealed into antistatic ESD bags. For SHT21S standard packaging sizes are 400, 1500 and 5000 units per reel. www.sensirion.com Each reel contains 440mm (55 pockets) header tape and 200mm (25 pockets) trailer tape. ...

Page 9

... Datasheet SHT21S Revision History Date Version 19 Aug 2009 0.6 4 March 2010 1.0 5 May 2010 1.1 Important Notices Warning, Personal Injury Do not use this product as safety or emergency stop devices or in any other application where failure of the product could result in personal injury. Do not use this product for applications other than its intended and authorized use ...

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