LSM6DSM: Increase in current draw once I2C lines are connected

[GTS.1]

Hi,

I have a MCU connected to a LSM6DSM using I2C with 1k pullups. I measured the average current consumption with the MCU and the LSM6DSM powered up but with the I2C lines physically disconnected. The current consumption was around 20uA.

Once I connected the I2C lines and measured the current consumption, it increased to 60uA. The LSM6DSM was not initialized at any point of time when I measured the current, so it's state would have been the same in both the scenarios.

What could cause this 40uA current draw? Is this to be expected?

Thanks

[Eleon BORLINI]

Hi @GTS.1​ ,

The current draw is a little high, but could be expected. Where you write "I2C lines are connected", do you refer to the I2C communication running or just to the physical connection? In the first case, the higher consumption is expected, and depends on the clock frequency (the higher the frequency, the higher the current consumption). And which are the default condition of these pads form the MCU point of view (PU, PD or open)?

What I can say you is that, by default, SCL and SDA pads have neither pull-up nor pull-down, from the sensor side.

-Eleon

[GTS.1]

Hi Eleon,

When I said "I2C lines are connected", I meant just the physical connections. There was no I2C communication happening in both the scenarios I had stated.

I'm not exactly sure what you meant when you asked about the default condition of the pads. The GPIOs are configured as inputs with no internal pull resistors configured. I have connected 1k ohm pullup resistors on the SDA and SCL lines though.

Thanks

[Eleon BORLINI]

Hi @GTS.1​ ,

thank you for the clarification, there should not be parasitic resistance paths on the I2C lines so far...

Could you please share the schematics of your application, especially the SDO/SA0 pad configuration?

If possible, you could you also try to increase the pull-up resistor values, for example from 1kOhm to 4.7kOhm or 10kOhm?

-Eleon

[GTS.1]

Hi @Eleon BORLINI​ ,

Is there any email ID on which I can share the schematics with you? I cannot post the schematics on a public forum.

Also, I tried 4.7k ohm and 10k ohm resistors too and still saw this issue.

Thanks

[Eleon BORLINI]

Understood...

You can send me an email

Thanks,

-Eleon

[GTS.1]

Hi,

I've mailed it you.

Thanks