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UCCx8C4x - soft start application

mburger
Intellectual 360 points
Other Parts Discussed in Thread: UC3843, UCC38C43

Hi,

We have a AC/DC power supply from a manufacturer which use the UC3843 but we are having some issues, so I want to try with a soft start to see if this could help us. My questions are:

1) does the UC3843 support this function as the UCCx8C4x does?

2) in case the answer is no, can I just remove the UC3843 and replace it with a UCC38C43 and add the extra circuitry for soft start feature?

3) can I use the 2n3906 instead of the 2n2907? I prefer to use SMD component for space saving.

4) for the diode, is ok to use the LL4148?

Best regards

Mark

  • 0
    TI__Expert 5900 points

    Hi Mark,

    Here are my suggestions.

    1)  and 2)Please refer to slua257 for the comparisons between UCCX8C4X and UCX84X, and the differences of parts of UCCX8C4X families

    www.ti.com/.../slua257.pdf

    UCCX8C4X is pin to pin compatible with UCX84X. Below are a comparison table

    To realize the soft start, both UC3843 and UCC38C43 need external circuits.

    In section 4.7 of Slua257, there is the example circuits for soft start.

    I think you could replace UC3843 with UCC38C43 and add soft start circuits.

    3) Yes, you can.

    4) Yes, you can.

    Br

    Kening