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TPS64201: Audible frequency using TPS64201

Samuel Tan
Prodigy 10 points
Part Number: TPS64201

Hi

I am using TPS64201 on my SPS with low load and I am hearing the audio frequency. The switching frequency is about 7-8khz, and the on-time is about 1.6usec. I read that TPS64201 will automatically reduce the on-time to as low as 200nsec  to ensure that switching frequency will be higher than 50Khz, so that we won't hear the audible sound.

Separately, I've another board with different layout but same schematic. The switching freq is about 24khz and on-time is 400nsec. I couldn't hear the switching freq on this board.

Can someone help to advise me where I could be missing out. 

Thanks and regards,

Samuel

  • 0
    TI__Genius 16590 points

    Hi Samuel,

    Could you please provide the below information:

    1. What is the load current you are using?
    2. If you vary the load current do you see the device shift to the smaller on times at some point?
    3. Does the second board have the same BOM and load current as the first?
    4. Can you please share schematics, layout and scope shots of the switch node and inductor current of both boards?

    Best regards,

    Varun

  • 0 in reply to Varun John
    Prodigy 10 points

    Hi Varun

    Thanks for responding. We found out that due to our capacitive load, the feedback voltage suffers from phase lag, resulting in longer turn-on time and as a result lower switching frequency in the audio range. The problem has been resolved. 

    Best regards,

    Samuel

  • 0 in reply to Samuel Tan
    TI__Genius 16590 points

    Hi Samuel,

    Thanks for the update. I shall go ahead and close this thread then.

    Best regards,

    Varun