AIS2IH datasheet(15/63 Pages) STMICROELECTRONICS

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3.2.2

Single data conversion on-demand mode

The device features a single data conversion on-demand mode which is valid for both sets of operating modes

(low-noise disabled or enabled) in the 4 low-power modes. This mode is enabled by writing the MODE[1:0] bits to

'10' in CTRL1 (20h). Low power modes are selected by writing the LP_MODE[1:0] bits in CTRL1 (20h).

The trigger for output data generation can be managed through the I²C/SPI or by applying a clock signal on the

INT2 pin acting here as an input by writing the SLP_MODE_ SEL bit in CTRL3 (22h):

•

When SLP_MODE_SEL = '0', output data generation is triggered by the clock signal on the INT2 pin (see

Figure 5).

•

When SLP_MODE_SEL = '1', output data generation starts when the SLP_MODE_1 bit is set to '1' logic

through the I²C/SPI. When XL data are available in the registers, this bit is automatically set to '0' and the

device is ready for another triggered session.

Output data are generated according to the selected low-power mode.

When output data is saved in an output register or FIFO, the device goes to power-down mode and waits for a

new trigger.

All ODRs in the range from 0 to up to 200 Hz are supported due to the INT2 clock input.

A DRDY signal or FIFO flags are available on the INT1 pin.

Power consumption is the same as that of standard low-power modes for the same ODR.

Figure 5. Single data conversion on-demand functionality

Trigger Signal (INT2 pin)

T_on

DRDY (INT1 pin)

At the end of turn-on time T_on, the DRDY interrupt is activated, output data are available to be read and the

device goes into power-down. T_on values depend on the low-power mode as follows:

T_on (typ.) =

•

1.20 ms for Low-Power Mode 1

•

1.70 ms for Low-Power Mode 2

•

2.30 ms for Low-Power Mode 3

•

3.55 ms for Low-Power Mode 4

3.2.3

Self-test

The self-test allows checking the sensor functionality without moving it. The self-test function is off when the

self-test bits (ST) are programmed to ‘00’. When the self-test bits are changed, an actuation force is applied to the

sensor, simulating a definite input acceleration. In this case the sensor outputs will exhibit a change in their DC

levels which are related to the selected full scale through the device sensitivity. When the self-test is activated, the

device output level is given by the algebraic sum of the signals produced by the acceleration acting on the sensor

and by the electrostatic test-force. If the output signals change within the amplitude specified in Table 3, then the

sensor is working properly and the parameters of the interface chip are within the defined specifications.

AIS2IH

Functionality

DS12421 - Rev 4

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