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LM4865: DC Vol/SD pin behavior

Kai Nomiyama
Expert 5285 points
Part Number: LM4865

Hi Audio team,

I have a question about DC Vol/SD pin behavior.

There are two case(①, ②) and depending on shutdown duration, LM4865 drives speaker or not.

Could you let me know maximum shutdown mode duration(max wait time) that can drive speaker?

①: No speaker driven

power up VDD --> DC Vol/SD > 1V --> below 300mV(shutdown mode) --> wait few msec --> DC Vol/SD > 1V

②: Speaker driven

power up VDD --> DC Vol/SD >1V --> below 300mV(shutdown mode) --> wait 20msec --> DC Vol/SD > 1V

Regards,

Kai

  • 0
    TI__Genius 17660 points

    Hello Kai, 

    Our team is looking into this thread and will respond as soon as possible. 

    Best Regards, 

    Justin Beigel

  • 0
    TI__Guru* 95225 points

    Hi Kai,

    There would be no maximum time limit to pull down SD pin.
    Could you elaborate on the conditions of the system? Do you mean when pulling SD pin low for short period the output is not working, but if pulling for a bit longer it works correctly?

    Best regards,
    -Ivan Salazar
    Applications Engineer - Low Power Audio & Actuators

  • 0 in reply to Ivan Salazar
    TI__Expert 5285 points

    Hi Ivan,

    Could you elaborate on the conditions of the system? Do you mean when pulling SD pin low for short period the output is not working, but if pulling for a bit longer it works correctly?

    --> correct, short SD pin low not working but longer SD pin low working.

    That's why customer wants to know the maximum time limit of pull down SD pin period. to avoid it.

    Regards,

    Kai

  • 0 in reply to Kai Nomiyama
    TI__Guru* 95225 points

    Hi Kai,

    You mean what is the minimum time SD pins has to be down to work properly, I suppose.

    The idea of this pin is to have a variable resistor connected, then no sudden changes like this would happen. It's possible that due to fast transition from highest to lowest DC levels the device is getting stuck in the mute or micro-power state.
    In addition, DC vol control is variable from device to device, unfortunately I would not be able to provide some specific time in this case.

    I would suggest to try on customer side with as many units as possible. 20ms seems to work for them, perhaps they can try shorter times like 10ms, 5ms or 1ms.

    Best regards,
    -Ivan Salazar
    Applications Engineer - Low Power Audio & Actuators