Specifications

BMA180

Preliminary data sheet

Bosch Sensortec

Rev. 1.0 Page 36 / - proprietary information - 06 March 2009

as copying and passing on to third parties. BOSCH and the symbol are registered trademarks of Robert Bosch GmbH, Germany.

Specifications within this document are preliminary and subject to change without notice. Document is not intended for publication.

7.9.3 lat_int

When this bit is at 1, interrupts are latched: the INT pad stays high until microprocessor detects

it and writes reset_int control bit to 1.

When this bit is at 0, interrupts are non-latched: interrupts are set and reset directly by BMA180

(e. g. interrupt condition disappears -> interrupt pin is reset to 0).

Following interrupts are influenced by lat_int:

- high high-g interrupt (high-g detection)

- low low-g interrupt (low-g or free-fall detection)

- slope slope or any-motion detection

- tap-sensing double tap detection

7.9.4 Low-g interrupt

7.9.4.1 General explanation

BMA180 is providing a possibility to detect free-fall or low-g values of a device.

Functionality is basically as follows: the sensor is measuring acceleration and comparing the

measured value with a certain predefined value. If acceleration is below this value and long

enough, a low-g interrupt is generated. If acceleration is above, no interrupt occurs. Sign of the

acceleration is also considered, thus absolute value is checked and compared to a given value.

Due to different devices (cell-phone, PND, lap-top, etc.) with different internal mechanical

constructions and placements of the sensor on a Printed-Circuit-Board (PBC), the sensor is

providing different parameters, the configuration of which is enabling device manufacturers to

optimize free-fall or low-g detection.

7.9.4.2 Low-g interrupt configuration parameters and settings

The following configuration parameters/settings are provided (all unsigned integer)

• low_int: This bit enables the low_th_criteria to generate an interrupt.

• low_th: defining low-g threshold value

• low_hy: defining associated low threshold hysteresis to prevent permanent inter-

rupt generation in case acceleration signal is too close to threshold value

• low_int_x: defining if low-g event on x-axis should generate low-g interrupt

• low_int_y: defining if low-g event on y-axis should generate low-g interrupt

• low_int_z: defining if low-g event on z-axis should generate low-g interrupt