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LM3881: power up pulse - how to pevent

Part Number: LM3881


Hi according ot he Datasheet the LM3881 will  during power up show a short pulse at the FLAG1-3 outputs because I assume the outputs follow the Vin independent on what EN PIN is telling.  IS this correct?

How can this be addressed if the device which should be controlled by the LM3881 is powered before the LM3881 and therefore the 0.65Volt could unintentionally be enable by the 0.65Volt pulse?

If there is a cap connected to the EN-PIN would the pulse at power up still occure?

  • Hi

    Yes, There is a spike(0.65V) when the VCC ramps. if this is a concern, you can have a divider on the FLAG pins  to reduce the amplitude of the FLAG to not enable the device controlled by LM3881.

    Regards
    Yihe