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

Part Number: LMZ12001
Other Parts Discussed in Thread: LMZ12003

Tool/software: WEBENCH® Design Tools


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,


  • 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 " 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.

  • Thank you for the reply Denislav