BQ24250: Problem with SYSOFF functionality

Hey Nikola,

I have a few questions so I can attempt to recreate this on our bench:

1) Is this on a custom board or are you using our EVM? If custom, can you provide a schematic?

2) Could you provide some test conditions (i.e. Battery voltage, VBUS voltage previous to removal, all register settings)?

With that, we can investigate further into your issue.

Regards,
Joel H

1) I am using board show on picture 

2) I checked control register and when I enter one byte into the REGISTER_6 and after that I read from this register I get the value that I wanted to write. For example, I write byte 0xb8 to REGISTER_6 after that when I read from REGISTER_6 I get same value (0xb8), but my battery doesn't interrupt the rest of the system

Best regards and many thanks,

Nikola

Hey Nikola,

By register settings, I mean the values of Registers 0x00 to 0x06 that you program onto the device, not just the SYSOFF bit.

I tried to repeat the test in our lab, but I did not see the same issue you are seeing. 

Is the VSYS voltage slowly collapsing? Or is it steady? You may attempt to add some bleed resistance in parallel to the VSYS output capacitance, to help drain it faster once Q4 is turned off.

Is it possible that there is still some at VBUS when you remove it? You may want to measure VBUS when you remove it in your test to ensure that there is no power source. 

Also, what is the pull-up rail to SDA/SCL (i2c lines)? Are you pulling up to a SYS rail or to a BAT rail?

Regards,

Joel H