BMA250 Bosch Sensortec, BMA250 Datasheet - Page 20

• Manufacturer Part Number: BMA250
• Description: 3-AXIS ACCELEROMETER DIGITAL I/F
• Manufacturer: Bosch Sensortec
• Series: -r

Specifications of BMA250

• Featured Product: BMA250 - Digital, Triaxial Acceleration Sensor
• Axis: X, Y, Z
• Acceleration Range: ±2g, 4g, 8g, 16g
• Sensitivity: 256LSB/g, 128LSB/g, 64LSB/g, 16LSB/g
• Voltage - Supply: 1.62 V ~ 3.6 V
• Output Type: I²C™, SPI™
• Bandwidth: 8Hz ~ 1kHz
• Interface: I²C, SPI
• Mounting Type: Surface Mount
• Package / Case: 12-VQFN
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant
• For Use With: 828-1024 - BMA250 DAUGHTERCARD FOR DEV KIT
• Other names: 828-1023-2

For slow and fast offset compensation, the compensation target can be chosen by setting the
bits (0x37) offset_target_x, (0x37) offset_target_y, and (0x37) offset_target_z according to table
11:
By writing ´1´ to the (0x36) offset_reset bit, all offset compensation registers are reset to zero.
4.6.1 Slow compensation
Slow compensation is a quasi-continuous process which regulates the acceleration value of
each axis towards the target value by comparing the current value with the target and adding or
subtracting a fixed value depending on the comparison.
The algorithm in detail: If an acceleration value is larger (smaller) than the target value (0x37)
offset_target_x/y/z for a number of samples (given by the parameter Offset Period see table 12),
the internal offset compensation value (0x38, 0x039, 0x3A) offset_filt_x/y/z or (0x3B, 0x03C,
0x3D) offset_unfilt_x/y/z is decremented (incremented) by 4 LSB.
The public registers (0x38, 0x039, 0x3A) offset_filt_x/y/z and (0x3B, 0x03C, 0x3D)
offset_unfilt_x/y/z are not used for the computations but they are updated with the contents of
the internal registers (using saturation if necessary) and can be read by the user.
The compensation period offset_period is set by the (0x37) cut_off bit as represented in table
12:
The slow compensation can be enabled (disabled) for each axis independently by setting the
bits (0x36) hp_x_en, hp_y_en, hp_z_en to ´1´ (´0´), respectively.
Slow compensation should not be used in combination with low-power mode. In low-power
mode the conditions (availability of necessary data) for proper function of slow compensation
are not fulfilled.
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.
offset_target_x/y/z
Table 12: Compensation period settings
Table 11: Offset target settings
(0x37)
Page 20 / not for publishing
00b
01b
10b
11b
cut_off
(0x37)
0b
1b
Data sheet
BMA250
Target value
Period
Offset
16
8
+1g
-1g
0g
0g
Bosch Sensortec
03 March 2011