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TPS25730: Is power path mandatory?

Tomasz Ciesla
Intellectual 690 points

Part Number: TPS25730
Other Parts Discussed in Thread: BQ25798

Tool/software:

Hi our PMs requested us to develop battery charger compatible with both USB-C to USB-C PD cable and USB-A to USB-C Quick Charge cable....(both supporting 12V 1.5A)

we use charging IC BQ25798 compatible with Quick Charge and I did some test with TPS25730 to enable it for PD 

I did connect CC1 and CC2 lines to TPS25730 and D+ and D- to BQ25798. It works but only when external power path of TPS25730 is always on (shorted). Both  USB-A to USB-C and  USB-C to USB-C cables (standards) can be used for 12V 1.5A charging.

Is it safe to operate this way? Datasheet of TPS25730 doesn't mention such mode of operation

  • 0
    TI__Mastermind 37976 points

    Hi Tomasz, 

    TPS25730 does not support QC schemes (does not have the capability to detect D+/D- enumeration from a QC source). If you short the external power path of TPS25730 this removes the OVP and RCP protection, details of the protection are shown below: 

    Supporting QC with USB-A to USB-C is not a standard supported by TPS25730, shorting across the external power path could allow the 12V to pass but this has not been tested on our end. 

    Thanks and Regards,

    Raymond Lin

  • 0 in reply to Raymond Lin
    Intellectual 690 points

    I did connect QC D+/D- line to BQ25798, and PD CC1 and CC2 to TPS25730. But the only way to make it work on both standards is to short the power path. The application is battery pack with integrated charger: we use discrete OVP and RCP from BQ25798

  • +1 in reply to Tomasz Ciesla
    TI__Mastermind 37976 points

    Hi Tomasz, 

    If the QC enumeration is being handled properly by BQ25798 along with OVP/RCP, then it should theoretically work. Just want to re-highlight that QC is not supported by TPS25730 and this implementation is not tested by us. 

    Another note to keep in mind, with the power path shorted there is always a direct path from the USB Type-C connector VBUS pin directly into the system (BQ25798). If a non-compliant connection is made (i.e. 12V upon connection), there is nothing in between the connector to the BQ25798 to prevent this scenario from happening. There may be other corner/niche cases to consider with this design. 

    Let us know if you have any further questions or concerns! 

    Thanks and Regards,

    Raymond Lin