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LM4871: Turn on transient?

Larry Rachman
Prodigy 70 points
Part Number: LM4871

We are experiencing a turn-on transient with the LM4871 when the STBY pin is driven active, causing a loud *pop* at the speaker.  A view of the two output lines shows that they come up approximately 22 msec apart, causing this transient. Is this normal behavior of the part? Is there anything that can be done to minimize the effect? Testing is being done with the device configured as a voltage follower, and the positive input held at VCC/2. The AUDIO_IN signal in the schematic is floating for test.

Our design operates the device configured as a  Sallen-Key filter, but even with the filter disabled (by removing C2) the behavior is the same.

  • 0
    TI__Mastermind 20085 points
    Hello Larry,

    Sometimes an unbalanced input in single-ended mode could cause pop noise. In order to avoid this issue the device could be used in differential mode, but due to your application, I don't think that this can be possible.
    This device is designed to work like an audio amplifier, I'm not sure that the device works properly in your application.
    I think that you can use an opamp to implement your application.

    Best Regards
    José Luis Figueroa
    Audio Applications Engineer