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WEBENCH® Tools/LMZ12001: LMZ12001/3 RC Enable sequencing

RoboScott
Prodigy 50 points
Part Number: LMZ12001
Other Parts Discussed in Thread: LMZ12003

Tool/software: WEBENCH® Design Tools

Hello, 

I am using LMZ12001 and LMZ12003 and want to sequence the turn on from lowest to highest (voltage output), what is current draw on the EN pin?  If I take into account the voltage threshold tolerance of EN can I use a RC circuit on the Enable ( is there any rise time that is too slow or any other limitations?)  

Thank you,


Scott

  • 0
    TI__Mastermind 18940 points
    Hello Scott,

    The LMZ1200x modules have a "precision" enable input, as opposed to logic level input. This allows you to precisely set the turn on threshold, using a resistive divider. Yes, you can also use an RC circuit to set the timing, or drive the EN input of the second regulator with the output of the first through a resistive divider.
    Keep in mind that each regulator will have certain softstart time, programmed by the softstart capacitor at the SS pin.

    See section "8.2.2.2 Enable Divider, RENT and RENB Selection" for more information on the divider selection.

    There is an internal pull-up current source on the EN pin for a default-on operation. I believe the current is around 6uA.

    Cheers,
    Denislav
  • 0 in reply to Denislav Petkov
    Prodigy 50 points
    Thank you for the reply Denislav