Regarding Switching On/Off LIS2DH12TR sensor

[KLakh]

Hi,

We are using LIS2DH12TR accelerometer sensor in our application. Attached is the circuit for the same. We are using a P-channel Mosfet part# BSS84W-7-F to switch the sensor on/off. We are able to switch On the sensor through the Mosfet but we are not able to switch it Off. We are able to get the sensor data on I2C lines read by the controller though we are turning it Off through the Mosfet. Do I need to select Chip select CS = 0 for completely turning it off ? We are getting supply or voltage at VDD/VDDIO even if we remove or unmount the Q1 mosfet and all the related resistors(R5,R8,R10,R11) whereas CS=1. When we keep CS=0, then we are not getting supply/voltage at VDD/VDDIO. Can you please help us to understand why is this phenomenon occuring ?

Waiting for your reply asap..

Regards,

Kamesh Lakhwani

[Eleon BORLINI]

Hi Kamesh @KLakh​ ,

>> Do I need to select Chip select CS = 0 for completely turning it off? 

This is a good point, or alternatively you could try leaving it floating from the application processor side.

Another suggestion could be to try to de-solder R1 and R3 and check the sensor condition.

In fact, the I2C lines should be pull-upped to the VddIO line, which I see is switched from the sensor side but not from the I2C lines.

Let me please know if these suggestion can help you for your purpose.

-Eleon

[STM-Hank]

Hi,

I think there may be a problem when you cut off the power supply to VDDIO when you have the I2C lines pulled up-which you shall. On the datasheet, there is a condition where the IO lines cannot exceed VDDIO+0.3V. this condition may be violated-Not sure what the consequence is?