Specifications

BMA180
Preliminary data sheet
Bosch Sensortec
Rev. 1.0 Page 38 / - proprietary information - 06 March 2009
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Specifications within this document are preliminary and subject to change without notice. Document is not intended for publication.
noise modes). Depending on ff_cd_r register value, the counter could also be reset or count
down when low_th_criteria is false:
ff_cd_r<1:0> Low-g interrupt counter (free-fall-counter) status
when low
_
th
_
criteria is false
00
reset
01
Count down by 1 N
COUNT
10
Count down by 2 N
COUNT
11
Count down by 3 N
COUNT
When the low acceleration interrupt counter value equals low_dur (low_dur <>0), an interrupt is
generated. If low_dur =0, an interrupt is generated as soon as the appropriate criteria is fulfilled.
The low_th_criteria is set with an AND condition on the three axis to be used as a free-fall
detection, thus acceleration signals of all 3 axes must be long enough below a certain thresh-
hold.
If latch_INT=0, the interrupt is not a latched interrupt (as in figure 6) and then it is reset as soon
as low_th_criteria becomes false. When interrupt occurs, the interrupt counter is reset.
7.9.5 High-g interrupt
7.9.5.1 General explanation
BMA180 is providing a possibility to detect high-g events 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 above this value long enough,
a high-g interrupt is generated. If acceleration is below, 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 high-g detection.
7.9.5.2 High-g interrupt configuration parameters and settings
The following configuration parameters/settings are provided (all unsigned integer)
• high_int: This bit enables the high_th_criteria to generate an interrupt.
• high_th: defining high-g threshold value
• high_hy: defining associated high threshold hysteresis to prevent permanent inter-
rupt generation in case acceleration signal is too close to threshold value