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Original question:

LMZM23601: start up delay

LMZM23601: Maximum voltage difference between EN pin and VIN pin

user5347034
Intellectual 320 points
Part Number: LMZM23601
Other Parts Discussed in Thread: LMZM33604, LMZM33603

Hello ,team members.

I want to delay the start-up by connecting a capacitor to the LMZM23601 EN pin.

I was advised in the previous thread that a schottky diode should be attached to the VIN-EN pin to discharge the capacitor.

However, because there are problems with schottky diodes, I want to use ordinary silicon diodes(Higer forward voltage).

So I would like to know how many volts the power supply voltage(VIN) can exceed the EN pin, if there is a specified value.

I would like to know if LMZM33603 and LMZM33604 have the specified voltage.

  • 0
    TI__Mastermind 47060 points

    Hi,

    I don't think there is a specific value that power supply can exceed EN pin. The Vin-to-GND and EN-to-GND absolute maximum rating is 42V however it is recommended to only run VIN at a maximum of 36V.

    You can always put a voltage divider on enable such that the discharge voltage onto input rail will never be above 42V. When the device is shut off and diode is installed, the stored voltage on the enable capacitor will discharge to the power supply and temporarily pump the input voltage up by the enable divider voltage. For example if you have a 36V input with a 10:1 resistor ratio on the EN pin with a diode connected between VIN and EN, when the power supply shuts off the input voltage will momentarily blimp to 36V + 3.6V which is 39.6V and within the absolute maximum rating of the input pin.

    Regards,

    Jimmy 

  • 0 in reply to Jimmy Hua
    Intellectual 320 points

    Hi, Jimmy.

    I understand.

    Many thanks for your help.

    Regards,