LPS27HHTW datasheet(34/55 Pages) STMICROELECTRONICS

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Figure 25. “Threshold-based” interrupt event

P_DIFF_IN

Negative

Threshold positive value

Threshold negative value

Positive

To enable the AUTOZERO mode, the AUTOZERO bit must be set to '1' and then the measured pressure value

is used as the reference and stored in the register REF_P (REF_P_L (15h), REF_P_H (16h)). From this point

on, the output pressure value (PRESS_OUT_XL (28h), PRESS_OUT_L (29h), PRESS_OUT_H (2Ah)) is updated

with the difference between the measured pressure and REF_P.

•

P_DIFF_IN = measured pressure - REF_P

•

PRESS_OUT = measured pressure - REF_P

After the first conversion, the AUTOZERO bit is automatically set back to '0'. In order to return back to normal

mode, the RESET_AZ bit in the INTERRUPT_CFG (0Bh) register has to be set to '1'. This also resets the content

of the REF_P registers to 0.

AUTOREFP mode allows using the pressure differential for the generation of the interrupt keeping the output

pressure registers PRESS_OUT (PRESS_OUT_XL (28h), PRESS_OUT_L (29h), PRESS_OUT_H (2Ah)) without

comparing REF_P. If the AUTOREFP bit is set to '1', the measured output pressure is used as the reference in the

•

P_DIFF_IN = measured pressure - REF_P

The output registers PRESS_OUT (28h, 29h and 2Ah) are not changed by REF_P and shows as follows.

•

PRESS_OUT = measured pressure

After the first conversion, the AUTOREFP bit is automatically set to '0'. In order to return back to normal mode, the

RESET_ARP bit has to be set to '1'

LPS27HHTW

INTERRUPT_CFG (0Bh)

DS13489 - Rev 1

page 34/55

LPS27HHTW Datasheet(PDF) 34 Page - STMicroelectronics