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LM25143-Q1: EN pin control under single output with dual phase structure

Evan Wang
Genius 9690 points
Part Number: LM25143-Q1

Hi TI expert,

May I know whether the ENx can be controlled separately under single output - dual phase structure?

We have to connect the mode/FBx/SSx pins accordingly but wondering whether we can pull low EN2 only in order to disable phase 2 under the same structure.   

We want to enable the phase 1 & phase 2 power in the sequence we want.

I notice someone ask similar questions recently but I need your confirmation on this part.

Thank you.

  • 0
    TI__Mastermind 22301 points

    Hi Chia,

    Yes that is correct, you can phase shed phase 2. However note that the datasheet says "The LM25143-Q1 in single-output interleaved operation does not support phase shedding when the output voltage is set between 0.6 V to 1.5 V."

    -Orlando

  • 0 in reply to Orlando Murray
    TI__Genius 9690 points

    Hi Orlando,

    Thank you for the confirmation.

    BTW, if we disable the EN2 in the first place during startup, then enable EN2 pin later.

    Will we expect to see a larger output ripple when phase 2 start to operate?

    Wondering whether internal mechanism will automatically wait for one cycle to enable the phase 2 power stage after we pull high the EN2 pin.

    => Scenario B

    Just in case IC will not follow the interleave operation during phase 2 startup and make entire output ripple a little bit larger at that moment.

    => Scenario A

    Below demo assume EN2 is enabled when iL1 is rising.

  • 0 in reply to Evan Wang
    TI__Mastermind 22301 points

    Hi Chia,

    EN will not immediately turn on the high-side FET. 

    Only the clock will turn on the FET, so it should be closer to scenario B.

    Hope this helps,

    -Orlando