BMA150 datasheet(53/56 Pages) BOSCH

53 / 56 page

Data sheet

BMA150

Triaxial, digital acceleration sensor

Bosch Sensortec

Rev. 1.6

Page 53

30 October 2008

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Note: Specifications within this document are subject to change without notice.

time

|a|

Freefall threshold

Evaluation duration

INT

low

high

Latched INT

High-g threshold

acceleration

Hysteresis

Reset INT

Figure 30: Explanation of freefall and high-g detection. Please see explanation within the text.

9.3 Any motion detection

The “any motion algorithm” can be used to detect changes of the acceleration. Thus it provides

a relative evaluation of the acceleration signals. The criterion is kind of a gradient threshold of

the acceleration over time. Thus one can distinguish between fast events with strong inertial

dynamic (e.g. shock), instant changes of force balance (e.g. drop, tumbling) and even slight

changes (e.g. touch of a mobile device).

Due to a high bandwidth and a fast response MEMS device the BMA150 is capable to detect

shock situations. The “any motion interrupt” or a high-g criterion setting can be used to give a

shock alert. The phase shift between onset of mechanical shock and interrupt output is defined

by the mechanical transfer function of the chassis and internal mounting interfaces (e.g. PDA

shell) and the data output rate of the sensor IC (currently 330µsec, 100µsec under

consideration).

BMA150 Datasheet(PDF) 53 Page - Bosch Sensortec GmbH