BQ25756: Reverse Mode Confusion

Part Number: BQ25756
Other Parts Discussed in Thread: BQ25750

This is a continuation of CS3033570, since the link to this ticket on the My Requests page under Customer Support leads to a "Requested record not found". That ticket is also marked as resolved but we would not consider it resolved.

How are you supposed to enter reverse mode? If Vsys is connected to VAC and reverse mode powers Vsys, VAC will see that as a valid input source and disable reverse mode. Even with VAC not connected to Vsys, all support forums we've read state to connect pin 32 and 33 which leads to pin 32 powering pin 33 with VAC_REV in reverse mode.

It makes sense to us that VAC shouldn't be connected to Vsys and pins 32 and 33 shouldn't be connected to each other. Pin 33 should be connected to a Vinput that connects to Vsys through a switch to allow charging but also be completely disconnected when we want to enter reverse mode. Pin 32 could be connected to Vsys in this scenario, assuming our understanding of that pin is correct. This contradicts most of the TI responses we've seen on the support forums, though.

  • Hi Nathan,

    When the device is in reverse mode, it does not register the power good state. This allows it to be in reverse mode with a voltage in the valid operating range.

    How are you supposed to enter reverse mode?

    Reverse mode can be entered via I2C when there is no input present. I2C is required to exit reverse mode as well.

    We have a power-path version of this device, BQ25750, where there is a switch between pin 32 and pin 33 if this fits your system requirements better. I2C is still required for reverse mode.

    Let me know if anything is still unclear.

    Best regards,
    Michael