PCM4104: Tone noise at Fs

Mochi

Part Number: PCM4104

Hello,

Our customer is trying to replace a DAC to PCM4104, during their ES unit evaluation they found tone noise at sampling frequency.

It looks like not related to digital filter "stop band attenuation" characteristics. Because tone noise is just on sampling frequency, not Fs+/-signal frequency point.

If input all "0" DATA, this tone noise is disappeared even analog noise floor is keeping same level.

When input 24bit LSB DATA like -140dB 1KHz signal, then sampling tone noise is generated.

Please refer attached captured images.

Is this caused by some analog noise coupling from DS modulator activity? But DS modulator clock might be 256fs or higher.

Regards,

Mochizuki

over 3 years ago

0 Paul_Frost over 3 years ago

TI__Guru 53453 points

Hi Mochizuki-san,

What is the SCK/LRCK ratio?

It is not very surprising to see a tone from the sample clock on the output, that is common on most of our older devices that did not have as advanced digital filters.

Thanks,

Paul

0 Mochi over 3 years ago in reply to Paul_Frost

Genius 3985 points

Hi Paul,

Thank you for your prompt reply.

The working condition is LRCK=44.1KHz and SCLK=256Fs.

Our customer understand may be this tone noise is caused by PCM4104 DF characteristics itself.

But request us to verify the noise on the EVM. Is it possible to duplicate it on your EVM?

Regards,

Mochizuki

+1 Paul_Frost over 3 years ago in reply to Mochi

TI__Guru 53453 points

Hi Mochizuki-san,

I do not have any hardware which I can test this with, but I am confident that this is expected.

Thanks,

Paul

Audio

Audio forum

PCM4104: Tone noise at Fs