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Original question:

[FAQ] TUSB320: Clarify DFP to Type-C 1.0 DRP incompatibility

TUSB320: TUSB320 ID keeps oscillating

Steve Hargreaves
Prodigy 10 points
Part Number: TUSB320

I'm using TUSB320 configured as DRP and I'm finding that (when nothing is connected to the USB-C connector) the ID output keeps oscillating between high and low at approximately 1Hz. Presumably this shouldn't be happening? I'd expect ID to only go low when a UFP device is plugged in?

  • +1
    TI__Mastermind 22605 points

    Hi Steve,

    You are correct that ID should only go low when a UFP is attached to the port.

    What behavior do you see on the CC1/2 lines? For a DRP, these pins should oscillate between high and low when nothing is connected

    Are you able to share the schematic of the 320 implementation? I can check to see if there are any problems with your configuration.

    Best,

    Shane

  • 0 in reply to Shane Hauser
    Prodigy 10 points

    Thanks Shane.

    You set me thinking about the CC lines, and I realised that we have a diode array (for ESD protection) that's preventing CC from rising above Vbus.

    Which is ok if Vbus is present, but behaves like the pulldowns of a ghost UFP device when Vbus is at 0V, giving rise to the oscillation.