BMA255 datasheet(13/119 Pages) BOSCH

13 / 119 page

BMA255

Data sheet

Page 13

BST-BMA255-DS004-05 | Revision 1.2 | August 2014

Bosch Sensortec

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.

4. Functional description

Note: Default values for registers can be found in chapter 6.

4.1 Supply voltage and power management

The BMA255 has two distinct power supply pins:

• VDD is the main power supply for the internal blocks

• VDDIO is a separate power supply pin used for supplying power for the interface

There are no limitations on the voltage levels of both pins relative to each other, as long as

each of them lies within its operating range. Furthermore, the device can be completely

switched off (VDD = 0V) while keeping the VDDIO supply on (VDDIO > 0V) or vice versa.

When the VDDIO supply is switched off, all interface pins (CSB, SDI, SCK, PS) must be kept

close to GNDIO potential.

The device contains a power-on reset (POR) generator. It resets the logic part and the register

values after powering-on VDD and VDDIO. Please note, that all application specific settings which

are not equal to the default settings (refer to 6.2 register map), must be re-set to its designated

values after POR.

There are no constraints on the switching sequence of both supply voltages. In case the I²C

interface shall be used, a direct electrical connection between VDDIO supply and the PS pin is

needed in order to ensure reliable protocol selection. For SPI interface mode the PS pin must

be directly connected to GNDIO.

BMA255 Datasheet(PDF) 13 Page - Bosch Sensortec GmbH