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Digital Humidity and Temperature Sensor - SHT21

Size: 3 x 3 x 1.1 mm
Output: I2C digital, PWM, SDM
Supply voltage range: 2.1 to 3.6 V
Energy consumption: 3.2μW (at 8 bit, 1 measurement / s)
RH operating range: 0 - 100% RH
T operating range: -40 to +125°C (-40 to +257°F)
RH response time: 8 sec (tau63%)

Model Number: SHT21
Data Sheet:

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Product Specification

SHT21 Digital Humidity and Temperature Sensor 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 1.1mm height it provides calibrated, linearized sensor signals in digital, I2C 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 (8/12bit up to 12/14bit 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.

SHT21 Digital Humidity and Temperature Sensor FEATURES
? Fully calibrated
? Digital output, I2C interface
? Low power consumption
? Excellent long term stability
? DFN type package – reflow solderable

SHT21 Digital Humidity and Temperature Sensor Performance
Relative Humidity

Parameter	Condition	Value	Units
Resolution	12 bit	0.04	%RH
Resolution	8 bit	0.7	%RH
Accuracy tolerance	typ	±2	%RH
Accuracy tolerance	max	see Figure 2	%RH
Repeatability		±0.1	%RH
Hysteresis		±1	%RH
Nonlinearity		<0.1	%RH
Response time	τ63%	8	s
Operating Range	extended	0 to 100	%RH
Long Term Drift	Typ.	< 0.25	%RH/yr

Temperature

Parameter	Condition	Value	Units
Resolution	14 bit	0.01	°C
Resolution	12 bit	0.04	°C
Accuracy tolerance	typ	±0.3	°C
Accuracy tolerance	max	see Figure 3
Repeatability		±0.1	°C
Operating Range	extended	-40 to 125	°C
Response Time	τ63%	5 to 30	s
Long Term Drift	Typ.	< 0.02	°C/yr

Electrical Specification

Parameter	Conditions	min	typ	max	Units
Supply Voltage, VDD		2.1	3.0	3.6	V
Supply Current, IDD	sleep mode	-	0.15	0.4	μA
Supply Current, IDD	measuring	200	300	330	μA
Power Dissipation	sleep mode	-	0.5	1.2	μW
	measuring	0.6	0.9	1.0	mW
	average 8bit	-	3.2	-	μW
Heater	VDD = 3.0 V	5.5mW, ΔT = + 0.5-1.5°C
Communication	digital 2-wire interface, I2C protocol

Other Series:

Series	Typ. Humidity Accuracy %RH	Typ. Temperature Accuracy °C	Supply Voltage Range V	Interface	Package Size (L x W x H) mm
SHT30	±2	±0.2	2.4 to 5.5	I2C, analog voltage	2.5 x 2.5 x 0.9
SHT31	±2	±0.2	2.4 to 5.5	I2C, analog voltage	2.5 x 2.5 x 0.9
SHT35	±1.5	±0.1	2.4 to 5.5	I2C	2.5 x 2.5 x 0.9
SHTW1	±3	±0.4	1.62 to 1.98	I2C	1.3 x 0.7 x 0.5
SHTW2	±3	±0.4	1.62 to 1.98	I2C	1.3 x 0.7 x 0.5
SHTC1	±3	±0.3	1.62 to 1.98	I2C	2 x 2 x 0.8
SHT20	±3	±0.3	2.1 to 3.6	I2C, PWM, SDM	3 x 3 x 1.1
SHT21	±2	±0.3	2.1 to 3.6	I2C, PWM, SDM	3 x 3 x 1.1
SHT25	±1.8	±0.2	2.1 to 3.6	I2C	3 x 3 x 1.1
SHT10*	±4.5	±0.5	2.4 to 5.5	Digital Sbus	7.5 x 4.9 x 2.6
SHT11*	±3	±0.4	2.4 to 5.5	Digital Sbus	7.5 x 4.9 x 2.6
SHT15*	±2	±0.3	2.4 to 5.5	Digital Sbus	7.5 x 4.9 x 2.6
SHT71	±3	±0.4	2.4 to 5.5	Digital Sbus	19.5 x 5.08 x 3.1
SHT75	±1.8	±0.3	2.4 to 5.5	Digital Sbus	19.5 x 5.08 x 3.1
*Not recommended for new design (NRND); newer products available