Bq24195 pull ups

Hi all- we’re currently trying to move from a boron platform to the new bsom. While we were laying out the pmic we saw that that i2c bus was pulled to the 3.3v regulator which is shut down by the EN pin. I guess I’m wondering how this works? We use the en pin to duty cycle our borons all the time and it does work well now(most of the time, sometimes the pmic bugs). if both the sda and scl are pulled down at the same time- then I think that’s fine, but if one is pulled down slightly before the other, then it can cause a start condition no? Are we really supposed to be releasing/pulling low the pull ups when we power the device down?

You are correct, the I2C line uses the 3V3 generated by the regulator as the pull-up voltage.

In theory this might cause activity on the bus - but we have never had any reports of this happening. There are many devices out in the field that are put to sleep using the EN pin.

The PMIC will be sitting idle if no further communication is received and uses very little power as-is.

What issues have you been seeing on the PMIC?
What version of DeviceOS are you using?
How is your device powered?

It’s not necessary to remove the pull-ups. The start bit is SDA falling before SCL. That seems unlikely in most cases even if it occurs, there will be an I2C timeout, which is handled by the bq24195. Since this probably only happens when you’re shutting down the MCU anyway, it’s unlikely that this will be a source of problems.

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