Specifications

BMA180
Preliminary data sheet
Bosch Sensortec
Rev. 1.0 Page 23 / - 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.
6.2 High-g logic
For indicating high-g events an upper threshold can be programmed. This logic can also be
activated by a control bit. Threshold, duration and reset behaviour can be programmed. The
high-g and free-fall criteria can be logically combined with an <OR>.
6.3 Slope detection (or 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 BMA180 is capable to detect
shock situations up to 1200Hz and 16g. The “any motion interrupt” or a high-g criterion setting
can be used to give a shock alert. The phase shift between start 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.
6.4 Tap sensing
Tap sensing feature is closely related to slope detection/any motion feature. Tap sensing is the
generation of an interrupt, if 2 slope detection events are detected within a shorten time. Tap
sensing is also known as double click. It is widely used in laptops to open software applications
via double click on a touch pad (on system level).
6.5 Alert Mode
Using the BMA180 it is possible to combine the “any motion criterion” with low-g and high-g
interrupt logic to improve the reaction time for e. g. free-fall identification. If alert mode is set,
free-fall or motion-counters are counting down earlier than without alert mode.
More information about alert mode is given in a separate application note (under preparation).