BMA400 I2C lines goes low once the power is cut-off

[Bimalsinh]

Hi,

We recently are facing issues as below:

- Our system is battery-operated and the IMU BMA400 sensor is powered by a power load switch. so when we need to turn on the IMU we will provide power and when we want to conserve power and BMA400 is not used in the application. we cut off the power from load switch.

- But when we do so. and cut off the power of BMA400, it drives the I2C lines also low, which prevents to access our other sensors in the system.

- Ideally, those pins may be an open drain pin, so when we cut off the power it shouldn't affect the I2C lines, but here it is pulling down the I2C lines as well.

Can you please explain this behaviour ? awaiting your reply for the same.

[BSTRobin]

Hi Bimalsinh,

We do not recommend using it this way: turn off the BMA400 power supply and continue communicating on I2C. Because theoretically the BMA400 power supply has been turned off, it is uncertain whether the high level on the I2C pin will affect the sensor. We have tested this and it is an abnormal operation.
If you do not use BMA400, you can set BMA400 to sleep mode, with a power consumption of only 160nA. For battery powered products, the current consumption is already very small.