3-AXIS ACCELEROMETER DIGITAL I/F

BMA250

Manufacturer Part NumberBMA250
Description3-AXIS ACCELEROMETER DIGITAL I/F
ManufacturerBosch Sensortec
Series-
BMA250 datasheets
 


Specifications of BMA250

Featured ProductBMA250 - Digital, Triaxial Acceleration SensorAxisX, Y, Z
Acceleration Range±2g, 4g, 8g, 16gSensitivity256LSB/g, 128LSB/g, 64LSB/g, 16LSB/g
Voltage - Supply1.62 V ~ 3.6 VOutput TypeI²C™, SPI™
Bandwidth8Hz ~ 1kHzInterfaceI²C, SPI
Mounting TypeSurface MountPackage / Case12-VQFN
Lead Free Status / Rohs StatusLead free / RoHS CompliantFor Use With828-1024 - BMA250 DAUGHTERCARD FOR DEV KIT
Other names828-1023-2  
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Page 33/74

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In order to avoid unwanted generation of the orientation interrupt in a nearly flat position (z ~ 0,
sign change due to small movements or noise), a hysteresis of 0.2 g is implemented for the z-
axis, i. e. a after a sign change the interrupt is only generated after |z| > 0.2 g.
4.8.8 Flat detection
The flat detection feature gives information about the orientation of the devices´ z-axis relative
to the g-vector, i. e. it recognizes whether the device is in a flat position or not.
The condition for the device to be in the flat position is
tan
Like blocking_theta, used with orientation recognition, the parameter_theta stands for a user-
defined setting. In this case the content of the (0x2E) flat_theta bits. The possible flat angles
also range from 0° to 44.8°. To ensure proper operation, parameter_theta has to be less than or
equal to blocking_theta.
The flat interrupt is enabled (disabled) by writing ´1´ (´0´) to bit (0x16) flat_en. The flat interrupt
is generated if the flat value has changed and the new value is stable for at least the time given
by the (0x2F) flat_hold_time bits. The flat value is stored in the (0x0C) flat bit if the interrupt is
enabled. This value is ´1´ if the device is in the flat position, it is ´0´ otherwise. The content of
the (0x0C) flat bit is changed only if the interrupt is generated. The interrupt is automatically
cleared after one sample period. Its status is stored in the (0x09) flat_int bit.
If temporary or latched interrupt mode is used, after the generation of the interrupt the changed
(0x0C) flat value is kept fixed as long as the interrupt persists (e. g. until the latch time expires
or the interrupt is reset). After clearing the interrupt, the (0x0C) flat value is only updated with
the next following value change (i.e. with the next occurring interrupt).
The meaning of the (0x2F) flat_hold_time bits can be seen from table 22.
Rev. 1.0
© Bosch Sensortec GmbH reserves all rights even in the event of industrial property rights. We reserve all rights of disposal such
as copying and passing on to third parties. BOSCH and the symbol are registered trademarks of Robert Bosch GmbH, Germany.
Note: Specifications within this document are subject to change without notice.
BMA250
Data sheet
parameter
_
theta
.
8
Table 22: Meaning of flat_hold_time
(0x2F)
Time
flat_hold_time
00b
0
01b
512 ms
10b
1024 ms
11b
2048 ms
Page 33 / not for publishing
Bosch Sensortec
03 March 2011