SHT21 SENSIRION, SHT21 Datasheet - Page 6

• Manufacturer Part Number: SHT21
• Description: Humidity/Temperture Sensor
• Manufacturer: SENSIRION

Specifications of SHT21

• Operating Temperature Range: -40°C To +125°C
• No. Of Pins: 6
• Supply Voltage: 3V
• Humidity Sensor Type: Capacitive
• Sensor Case Style: DFN
• Humidity Range: 0% To 100%
• Response Time: 8s
• Accuracy: ± 2%
• Supply Current: 300µA

Datasheet SHT21
3 Interface Specifications
Table 2 SHT2x pin assignment, NC remain floating (top view)
3.1
The supply voltage of SHT2x 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 – see Figure 11.
3.2
SCL is used to synchronize the communication between
microcontroller (MCU) and the sensor. Since the interface
consists of fully static logic there is no minimum SCL
frequency.
3.3
The SDA pin is used to transfer data in and out of the
sensor. For sending a command to the sensor, SDA is
valid on the rising edge of SCL and must remain stable
while SCL is high. After the falling edge of SCL the SDA
value may be changed. For safe communication SDA shall
be valid t
edge of SCL, respectively – see Figure 12. For reading
data from the sensor, SDA is valid t
low and remains valid until the next falling edge of SCL.
Figure 11 Typical application circuit, including pull-up resistors
R
To avoid signal contention the micro-controller unit (MCU)
must only drive SDA and SCL low. External pull-up
resistors (e.g. 10kΩ), are required to pull the signal high.
For the choice of resistor size please take bus capacity
requirements into account (compare Table 5). It should be
noted that pull-up resistors may be included in I/O circuits
www.sensirion.com
Pin Name
3,4
1
2
5
6
P
and decoupling of VDD and VSS by a capacitor.
SCL OUT
SDA IN
SDA OUT
SCL IN
MCU (master)
SDA Serial Data, bidirectional
VDD Supply Voltage
VSS Ground
SCL Serial Clock, bidirectional
Power Pins (VDD, VSS)
Serial clock (SCL)
Serial SDA (SDA)
NC
SU
and t
Not Connected
HD
Comment
before the rising and after the falling
R
P
R
P
VDD
SCL
SDA
GND
VD
4
5
6
after SCL has gone
SHT2x
(slave)
Version 1.1 – May 2010
3
2
1
of MCUs. See Table 4 and Table 5 for detailed I/O
characteristic of the sensor.
4 Electrical Characteristics
4.1
The electrical characteristics of SHT2x are defined in
Table 1. The absolute maximum ratings as given in Table
3 are stress ratings only and give additional information.
Functional operation of the device at these conditions is
not implied. Exposure to absolute maximum rating
conditions for extended periods may affect the sensor
reliability (e.g. hot carrier degradation, oxide breakdown).
Parameter
VDD to VSS
Digital I/O Pins (SDA, SCL)
to VSS
Input Current on any Pin
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
(Charged Device Model, 750V corner pins, 500V other
pins). Latch-up immunity is provided at a force current of
100mA with T
For exposure beyond named limits the sensor needs
additional protection circuit.
4.2
The electrical characteristics such as power consumption,
low and high level input and output voltages depend on
the supply voltage. For proper communication with the
sensor it is essential to make sure that signal design is
strictly within the limits given in Table 4 & 5 and Figure 12.
Parameter
Output Low
Voltage, VOL
Output High
Voltage, VOH
Output Sink
Current, IOL
Input Low
Voltage, VIL
Input High
Voltage, VIH
Input Current
Table 4 DC characteristics of digital input/output pads. VDD =
2.1V to 3.6V, T = -40°C to 125°C, unless otherwise noted.
Absolute Maximum Ratings
Input / Output Characteristics
ESD-STM5.3.1-1999
amb
VDD = 3.0 V,
-4 mA < IOL < 0mA
VDD = 3.6 V,
VIN = 0 V to 3.6 V
= 125°C according to JEDEC JESD78.
Conditions
-100
min
-0.3
-0.3
70%
VDD
70%
VDD
min
0
0
-
-
and
VDD + 0.3
max
100
typ
-
-
-
-
-
-
5
AEC-Q100-011
VDD
VDD
VDD
30%
max Units
0.4
±1
-4
Units
mA
V
V
mA
uA
V
V
V
V
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