Specifications

BMA180
Preliminary data sheet
Bosch Sensortec
Rev. 1.0 Page 50 / - 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.
7.10.4 tc0_x, tc0_y and tco_z
These 18 bits (6 bits each axis) are used to realize the temperature compensation of the offset
on each axis. This compensation is directly done in the digital part.
TCO-correction for each channel could be min. -1.6 mg/K for max. TCO, 0 mg/K for no TCO and
max. +1.6 mg/K for min TCO. Step-size is 0.05 mg/K, thus all intermediate steps could be
calculated easily.
Theoretically a remaining TCO of only 0.025 mg/K could be the result. Assuming a linear TCO
across the whole temperature range (-40 °C .. +85 °C), theoretically a remaining minimum offset
of approximately ±1.5 mg could be the result. Due to small non-linearities (NL-TCO), etc. final
TCO and thus final remaining offset is slightly higher.
7.10.5 tco_range
By setting this bit to ‘1’, TCO range changes from ±1.6 mg/K to ±6.4 mg/K, TCO step size
changes from ±0.05 mg/K to ±0.20 mg/K.
7.10.6 tcs, tcs_only_z
The 4 tcs-bits are used to provide a temperature compensation of the sensitivity for all axes
(trimming range: -4% . . . +3.5% for the whole temperature range). All 3 g-axes are
compensated identically, if tcs_only_z = 0 (this bit is hidden in Bosch reserved area of
EEPROM). In this case a different trimming for a different axis is not possible. If tcs_z_only = ‘1’,
tcs is only influencing z-axis. Setting of tcs_z_only is done in Bosch production line. Typically
tcs_z_only is set to ‘1’, thus only TCS of z-axis can be recalibrated.
The compensation is done with respect to room temperature (approx. 25°C). The devices are
pre-trimmed in production line, but if lowest TCS is necessary, trimming after soldering might
optimize TCS. This trimming could be performed in-line by device manufacturer.
The following table informs about the signal correction by using the tcs-bits (correction
corresponds to a full temperature range correction from -40°C up to +85°C. As a consequence a
correction of approx. ±2% with respect to room temperature (+25°C) is possible.
tcs<3:0> Full temp (-40°C to +85°C)
correction
0
-4,0%
1
-3,5%
2
-3,0%
3
-2,5%
4
-2,0%
5
-1,5%
6
-1,0%
7
-0,5%
8
0,0%
9
0,5%
10
1,0%
11
1,5%
12
2,0%
13
2,5%
14
3,0%
15
3,5%