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UCC2800: Will grounding the FB pin disable the internal soft start mechanism of the IC?

Joel Stephen Prabhakar Kurati
Prodigy 10 points
Part Number: UCC2800

Tool/software:

Hi all,

I am trying to use the UCC2800 for an opto isolated flyback converter application. I am used to typically grounding the FB pin (the inverting input of the Error Amplifier) to disable the Error Amplifier and directly connect the COMP pin to the optocoupler's collector in common emitter configuration. My question is regarding the soft start. Will grounding the FB pin disable the internal soft start mechanism of the IC? 

Thanks,

Joel.

  • +1
    TI__Guru 73495 points

    Hi,

    No, ground FB does not disable internal soft start. Soft start is tested with FB = 1.8V < REF/2 = 2V (3, 5) or 2.5V (0, 1, 2, 4,), so IC will behave quite the same for FB < = 1.8V. Soft start will be kept when power on with FB grounded.