HTS221 datasheet(23/33 Pages) STMICROELECTRONICS

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HTS221

7.4

CTRL_REG2 (21h)

Control register 2

The BOOT bit is used to refresh the content of the internal registers stored in the Flash

memory block. At device power-up, the content of the Flash memory block is transferred to

the internal registers related to trimming functions to permit good behavior of the device

itself. If, for any reason, the content of the trimming registers is modified, it is sufficient to

use this bit to restore the correct values. When the BOOT bit is set to ‘1’ the content of the

internal Flash is copied inside the corresponding internal registers and is used to calibrate

the device. These values are factory trimmed and are different for every device. They permit

good behavior of the device and normally they should not be changed. At the end of the

boot process, the BOOT bit is set again to ‘0’.

The ONE_SHOT bit is used to start a new conversion. In this situation a single acquisition of

temperature and humidity is started when the ONE_SHOT bit is set to ‘1’. At the end of

conversion the new data are available in the output registers, the STATUS_REG[0] and

STATUS_REG[1] bits are set to ‘1’ and the ONE_SHOT bit comes back to ‘0’ by hardware.

The Heater bit is used to control an internal heating element, that can effectively be used to

speed up the sensor recovery time in case of condensation. The heater can be operated

only by an external controller, which means that it has to be switched on/off directly by FW.

Humidity and temperature output should not be read during the heating cycle; valid data can

be read out once the heater has been turned off, after the completion of the heating cycle.

Typical power consumption related to VDD is described in Table 18.

76543210

BOOT

Reserved

Heater

ONE_SHOT

[7]

BOOT: Reboot memory content

(0: normal mode; 1: reboot memory content)

[6:2]

Reserved

[1]

Heater

(0: heater disable; 1: heater enable)

[0]

One-shot enable

(0: waiting for start of conversion; 1: start for a new dataset)

Table 18. Typical power consumption with heater ON

VDD [V]

I [mA]

3.3

2.5

1.8

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