SI7021-A20 Datasheet, PDF (25/36 Pages) Silicon Laboratories – IC HUMIDITY AND TEMPERATURE SENSOR

Si7021-A20
5.5. Heater
The Si7021 contains an integrated resistive heating element that may be used to raise the temperature of the
sensor. This element can be used to test the sensor, to drive off condensation, or to implement dew-point
measurement when the Si7021 is used in conjunction with a separate temperature sensor such as another Si7021
(the heater will raise the temperature of the internal temperature sensor).
The heater can be activated using HTRE, bit 2 in User Register 1. Turning on the heater will reduce the tendency
of the humidity sensor to accumulate an offset due to "memory" of sustained high humidity conditions. Several
different power levels are available. The various settings are adjusted using the Heater Control Register and are
described in the following table.
Table 13. Heater Control Settings
HEATER[3:0] Typical Current
Draw^* (mA)
0000
3.09
0001
9.18
0010
15.24
...
...
0100
27.39
...
...
1000
51.69
...
...
1111
94.20
*Note: Assumes V_DD = 3.3 V.
Rev. 1.1
25