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UCC28070: Use SS Pin to Control Enable and Disable

Francis Jiang
Intellectual 1670 points
Part Number: UCC28070
Other Parts Discussed in Thread: UCC28065, UCC25660

Tool/software:

Hi Team,

Customer is asking whether UCC28070 can use SS pin to control enable and disable. I think this device can and provide below explanation, but he further ask whether there is a reference design which uses this function. Could you please help provide it? Thanks in advance.

BRs

Francis

  • +1
    TI__Mastermind 44620 points

    Hi Francis,

    We do not have a reference design implemented the shutdown of the UCC28070 at the moment. One possible implementation would be to use the TSET pin of the UCC25660 LLC controller drive a 2N7002 n-channel FET To pull dow the SS pin when it enters into light load.

    I hope this answers your question.

  • 0 in reply to JCHK
    TI__Intellectual 1670 points

    Hi JCHK,

    Sorry for trouble, are you attach the right material? Firstly, the document is not UCC25660 but is UCC28065. Secondly, I don't find both two devices have SS pin or the EVM user's guide has a FET used for pulling down.

    Could you please help check it again? And could you please help provide the picture of schematic directly on the E2E? Thanks a lot.

    BRs,

    Francis

  • +1 in reply to Francis Jiang
    TI__Mastermind 44620 points

    HI Francis,

    I am sorry my previous response was not clear. My meaning was to use the UCC25660 LLC as the second stage after the PFC.

    For thge UCC28065, soft-start is controlled with the COMP pin. How this works is described here:

    For the LLC controller, the UCC25660, soft-start is controlled internally. It does this to avoid a noisy layout from inducing noise that could fool another controller to prematurely exit soft start. This is described here:

    Here is an example of how to use the TSET pin to automatically disabled the UCC28065 which the UCC25660 enters into a light load condition. 

    I hope this clarifies your question.