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LM27762: Current requirements for output enable pins

Mark Cohen
Prodigy 60 points
Part Number: LM27762


My proposed application, in a battery-operated design, uses a pull-up resistor for the enable pins on the LM27762, that is grounded when powered off. It is important to the application to minimize the current draw when the device is off.

Unfortunately, I was unable to find any specs on the enable pin current requirements, or on its effective input resistance. Without WEBENCH, I'm unable to simulate this.

Can you tell me, please, how much current is required to enable the output? Alternatively, would you have a suggested value for a pull-up resistor that would supply adequate current to keep that pin above the 1.5V threshold when connected to a 3.5V source?

Thanks for your help.

I'd also be grateful to anyone who would care to comment on this layout. 0805 resistors were used for programming (R2 and R4 in my schematic), simply to make it easier to alter output voltage by hand.

    

  • 0
    TI__Expert 7695 points

    Hi User,

    Thanks for your question.

    I will check on the bias current requirement and let you know by Wednesday.

    Thanks,

    Stefano

    All information in this correspondence and in any related correspondence is provided “as is” and “with all faults”, and is subject to TI’s Important Notice (http://www.ti.com/corp/docs/legal/important-notice.shtml).

  • 0 in reply to Stefano Panaro
    TI__Expert 7695 points

    Hi User,

    Unfortunately we don´t have specific data on the maximum current absorption of the EN pin.

    However, we usually advise a pull up resistor in the range of 100kohm - 1Mohm.

    Please test the desired resistor in your specific application, but you should be ok if you use these values.

    I don´t see any particular concerns with the layout, since it is very similar to the reference one.

    I would advise you to maximize the number of vias connection to the GND plane, when possible.

    Please ask again if you need further support. 

    Thanks,

    Stefano

    All information in this correspondence and in any related correspondence is provided “as is” and “with all faults”, and is subject to TI’s Important Notice (http://www.ti.com/corp/docs/legal/important-notice.shtml).