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Original question:

TPS25750: Technical questions for TPS25750 + BQ25792

TPS25750: Auto disabling OTG on BQ25730/BQ25731 when usb-c plug is not present

Richard TAUPIAC
Prodigy 210 points
Part Number: TPS25750
Other Parts Discussed in Thread: BQ25730, , TPS25751

Hi,

We use the couple TPS25750 + BQ25730 to manage a product on battery. In order to save as much power as we can when our device is powered off, we try to disable the OTG supply in our BQ by using the register bit EN_OTG. When shutting down the device, we set this bit to 0. But I noticed if we plug a USB drive on our device, it seems to be enabled again. We monitor our battery current, and it's going up to the same level as when OTG is active. We suspect the TPS to automatically enable the OTG bit when something is plugged.

We would like to know if there is a way to prevent the TPS to auto enable OTG, until we allow it again ?

Or, second option for us, would it be possible for the TPS25750 to automatically disable the OTG when the USB drive is unplugged (because our system will be powered off so our processor unit cannot react to the "unplugged" event the TPS fires) ?

That second choice is not the best, but at least if a USB drive was plugged then removed while our device is off, it would fall down to a minimal consumption level again and save some battery.

Thanks and regards,

Richard

  • +1
    TI__Mastermind 25596 points

    Hi Richard, 

    When TPS25750 detects a sink device (TPS25750 is acting in a source power role) attached it will automatically enable OTG mode on the BQ25730/1 for sourcing. Once enabled we do not configure OTG mode again unless a Power On Reset event occurs. If the PD ever switches power role it will configure the forward mode of BQ25730/1 which overrides the OTG mode bit of the BQ. 

    For future designs we recommend switching over to TPS25751, it is pin-to-pin with TPS25750 and includes new firmware patches, features such as PPS and supports PD3.1 specification. 

    Thanks and Regards,

    Raymond Lin

  • 0 in reply to Raymond Lin
    Prodigy 210 points

    Hi Raymond,

    Thank you a lot for your detailed answer.

    What do you mean by TPS25751 "includes new firmware patches" ? What are the fixes implemented ?

    Thanks and regards,

    Richard

  • +1 in reply to Richard TAUPIAC
    TI__Mastermind 25596 points

    Hi Richard, 

    For example there was a bug where the PD (TPS25750) will always configure the attached BQ device to set IOTG to 3A regardless of what the Type-C current advertisement was set to. This was mentioned in a separate e2e thread and since has been addressed and implemented in TPS25751. Patches/fixes also include updates for meeting PD3.1 specification, updated configurations for supported BQ devices, more registers to configure through the Application Customization Tool, etc.

    TPS25751 also supports new feature such as PPS source and sink and Liquid Detection/Corrosion Mitigation. These new features are implemented through a combination of hardware and firmware updates. 

    Let me know if there's any further questions or concerns! 

    Thanks and Regards,

    Raymond Lin