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TPS25820: review

kevin.huang_FJXM
Expert 2925 points
Part Number: TPS25820

hi Teams:

Please help review the schematic diagram below. Thank you.

1. The input is USB-A and the output is USB-C. Now, it is required that the output USB-C has no power when not connected to Device, and only when connected to Device does it have power

2. Can pass USB-C certification

Also, may I ask if the device connected to the backend USB-C port is non-standard and does not have CC, then it cannot be used? Thank you.

3. Should the CHG pin be raised to provide 1.5A current to the device? If the CHG is lowered and connected to a USB-C 2.0 device, can it only provide 500mA current? Thank you.

  • 0
    TI__Expert 8785 points

    Kevin,

    USB expert will provide you answers by the end of this week.

    Thanks,

    Chris

  • 0 in reply to Christodulos Tsongas
    TI__Genius 12785 points

    Hello Kevin,

    kevin.huang_FJXM said:
    The input is USB-A and the output is USB-C. Now, it is required that the output USB-C has no power when not connected to Device, and only when connected to Device does it have power

    In order to be USB-C compliant you need to guarantee that VBUS on the USB-C port is always <= 4.75V.  The VBUS on the USB-A input could be lower than that, so you can’t guarantee 4.75V.   Guaranteeing USB-IF compliance would mean adding a DC/DC boost.   But the TPS25820 will disable VBUS when nothing is connected, so there isn’t any issue as far as that goes.

    kevin.huang_FJXM said:
    Can pass USB-C certification

    No, without a DC/DC you can’t meet the VBUS > 4.75V requirement. 

    kevin.huang_FJXM said:
    Also, may I ask if the device connected to the backend USB-C port is non-standard and does not have CC, then it cannot be used? Thank you.

    The TPS25820 doesn’t need the attached sink to communicate anything. It is up to the sink to read and interpret the CC voltage.

    kevin.huang_FJXM said:
    Should the CHG pin be raised to provide 1.5A current to the device? If the CHG is lowered and connected to a USB-C 2.0 device, can it only provide 500mA current? Thank you.

    The current limit is always 1.67A regardless of the CHG pin state, so it can always deliver that much power.  So the CHG pin only changes what capability is broadcast.  See table from data sheet. The sink should see the capability that is broadcast and set its load accordingly, but regardless the TPS25820 will set the current limit to 1.67A.

    Best Regards,

    Christian.