Specifications

BMA180

Preliminary data sheet

Bosch Sensortec

Rev. 1.0 Page 31 / - proprietary information - 06 March 2009

as copying and passing on to third parties. BOSCH and the symbol are registered trademarks of Robert Bosch GmbH, Germany.

Specifications within this document are preliminary and subject to change without notice. Document is not intended for publication.

7.8.3 mode_config

BMA180 has four different working sub-modes in “standard mode”. By setting the mode_config

bits the sub-mode is configured as described in the following table.

mode_config <1:0> Description

00 (default) Low noise mode -> highest current, low noise, full bandwidth

(1200 Hz)

01 Super low noise mode with reduced bandwidth -> highest

current, almost lowest noise, reduced bandwidth (300 Hz)

10 Ultra low noise mode with further reduced bandwidth, slightly

smaller current compared to mode 01-> almost highest

current, ultra- lowest noise, reduced bandwidth (150 Hz);

furthermore: output data rate = 1200 samples/sec.

11 Low power mode -> BW is decreased by factor 2, lowest

power, noise higher than in low noise modes

00b, 01b and 11b are the main configuration modes. 10b is considered as intermediate

configuration mode (intermediate in terms of either noise level or current consumption).

Important remarks:

• When bw is decreased by 2 for mode 11b, all timings used by the digital functions and

the system clock frequency remain related to the bw.

• Any change of the mode_config bits results in transient behaviour of the measured

acceleration values. The length of the transient response depends on the selected

bandwidth. Also some spurious interrupts might be generated as a result of the

mode_config change.

• The length of the transient response corresponds to an appropriate number of

acceleration samples to be acquired. This number of samples is depending on the

chosen filter bandwidth and is shown below.

Bandwidth 120

600 300 150 75 40 20 10

Nr. of samples 0 6 9 18 35 64 127 253

• The sensor is calibrated for mode_config = “00”. By changing to other modes, the offset

is changed too, thus subsequently an offset correction has to be performed. This could

be done by offset fine-tuning the device during in-line calibration.

• It is highly recommended not to change mode_config within an application. In this case,

offset fine-tuning is still working, but it is not ensured, that the device is properly placed

during calibration. If the device is e. g. used in ultra-low noise mode, bandwidth is limited

and highest current consumption could be measured. In order to save current, a frequent

switching from operation to sleep mode and back could be used (as already described in

section 4.2). This is no problem for most of the applications.