LM49352 MCLK requirements

Robert Sefton

We're using the LM49352 with the PLL off and the I2S ports as slaves. Does MCLK have to be frequency-locked to WCLK and BCLK? Or can it have an independent time base? In our system the audio sample clocks (WCLK and BCLK) will be locked to an external reference, but we would like to be able to generate MCLK locally without locking it to the same external reference. It's not clear (to me anyway) from the data sheet what the requirements are.

Thanks.

over 10 years ago

0 Andy Liu (BMS) over 10 years ago

TI__Guru 52115 points

Hi Robert,

I will try to find the answer for you.

Andy

0 Robert Sefton over 10 years ago in reply to Andy Liu (BMS)

Prodigy 80 points

Hi Andy -

Thanks for the quick response. Much appreciated. I look forward to the answer.

Bob

0 Andy Liu (BMS) over 10 years ago in reply to Robert Sefton

TI__Guru 52115 points

Hi Robert,

My colleague who is an expert on these LM audio devices are now on vacation, so a direct answer will be available very soon. I will have to verify this issue with one LM49352EVM board in my office, which might take one or two days.

Andy

0 Andy Liu (BMS) over 10 years ago in reply to Andy Liu (BMS)

TI__Guru 52115 points

Hi Robert,

I have just found an app note, which might answer your question. Take a look

www.ti.com/.../slaa469.pdf

Andy

0 Robert Sefton over 10 years ago in reply to Andy Liu (BMS)

Prodigy 80 points

Hi Andy -

That app note makes it clear that MCLK must be frequency-locked to the audio sample clocks otherwise samples will eventually have to be dropped or repeated to compensate. So that answers my question.

Thanks!

Bob

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LM49352 MCLK requirements