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LMZ31704: Inhibit (INH) control, LMZ317xx

Part Number: LMZ31704

Hi support team,

I have a question about page 21 of SLVSBV8E.
"The INH pin has an internal pullup current source, allowing the user to float the INH pin for enabling the device.
If an application requires controlling the INH pin, use an open drain/collector device, or a suitable logic gate to interface with the pin."

Is it a problem to input INH push-pull signal and input High when Enable?

Regards,
Dice-K

  • Hi Dice-K,

    There is no issue driving the INH pin with a push-pull signal.

    Anthony

  • Hi Anthony,
    Thank you for your reply.

    Confirmation about INH pin.

    Is it an issue to pull up 3.3V externally?
    The internal power supply will be biased from the outside.

    It seems to have a 2.9V pull-up inside.

    note (5), page-5, SLVSBV8E
    "When the device is operating and no UVLO resistor divider is present on this pin, the open voltage is typically 2.9 V."

    Best regards,
    Dice-K

  • No issue with pulling up to 3.3V externally. The external source just needs to be within the abs max ratings of the pin. We usually, if not always, evaluate startup through this pin by driving it with a step from a function generator

    The pin comes up to 2.9V through the internal current sources on the pin that allow the part to startup with the pin floating. The 2.9V is just the limit of the internal bias generating the current sources. It is ok to overdrive these internal current sources.