TAS3251: TAS3251 Pop Noise

user4991603

Part Number: TAS3251

Hello,

I have the TAS3251EVM here and when I turn on the Board in the sequence that is described in the manual I always get an audible noise out of the loudspeakers when I flip the RESET_AMP switch S3 to normal on the board.

The same also happens when S3 is in the 'normal' position before I apply power to the amp.

Changing the value of the CSTART capacitor didn't change anything. I thought that CSTART might have an influence on the softstart behaviour of the amp.

Except the CSTART capacitor, we didn't change anything on the board. The amp on the board works in BTL-mode with 2 loudspeakers connected to it.

I wonder if the pop prevention function actually works satisfiably on the TAS3251 as another person complained about it too in another thread:

https://e2e.ti.com/support/audio-group/audio/f/audio-forum/1159617/tas3251-pop-noise/

I is also have another question about the TAS3251EVM:

it looks like there is a feedback network consisting of 4 parts per phase that are unpopulated and where I can't find any info about it in the manual.

What is the feedback network for?

Thanks in advance,

Stephan

over 1 year ago

0 Jesse Ji over 1 year ago

TI__Genius 11300 points

Hi Stephan

1.Cstart is a timing capacitor, it increase the start up time to prevent the output signal been outputted too fast so that the pop happen.

when you change the Cstart, can you take a measurement for C_start and Spk_Out + and -, you can compare before and after to see whether the signal rising time change at Cstart pin.

2. using a multimeter or oscilloscope measure the voltage difference at spk_out+ and - when pop happened. multimeter can only get a max DC offset. oscilloscope can get a wavform, it might be better.

3. the feedback network is a Post-filter feedback circuit. if you think the performance of the amp cannot satisfy the request, it might be a choise.

below link describe more detail.

https://www.ti.com/lit/an/slaa788a/slaa788a.pdf?ts=1670291086324&ref_url=https%253A%252F%252Fwww.ti.com%252Fsitesearch%252Fen-us%252Fdocs%252Funiversalsearch.tsp%253FlangPref%253Den-US%2526searchTerm%253DTPA324x%2Band%2BTPA325x%2BPost-Filter%2BFeedback%2526nr%253D22

thanks.

jesse

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TAS3251: TAS3251 Pop Noise