PCM1794A Noise@260kHz and 125MHz

Kuramochi Tadahiko

Guru 28715 points

Other Parts Discussed in Thread: PCM1794A

Hi,

My customer is evaluating PCM1794A on the typical application circuit.

They has a trouble of noise, and we're checking the cause.

The noise is seen on the output of the I/V amp and Diff/Signal amp.

The frequency of the noise is 260kHz and 125MHz.

For the measurement circuit and waveforms and CLK freq etc, please refer the attached file.

The following is my question.

・Does the PCM1794A have the oscillator(i.e. PLL) regarding 260kHz of 125MHz?

Please let me know if you have the supposed cause or the experiment.

PCM1794A.xlsx

Thanks and Regards,

Kuramochi

over 10 years ago

0 Don Dapkus over 10 years ago

TI__Guru**** 189401 points

Hi, Kuramochi-san,

It will take us some time to investigate this with you. I expect about a week to get some results.

Please let us know in the meanwhile if you find any more information before then.

-d2

0 Justin Bohr over 10 years ago in reply to Don Dapkus

TI__Mastermind 27990 points

Hi Kuramochi-san,

Thank you for the detailed waveform and schematic with HW control settings. Is this noise the only output you get or is this noise that is on top of your signal? Have you confirmed that your data coming in is right justified? The standard setting (your current setting) is right justified PCM data. have you tried this with a known good audio source?

There are no internal supplies that create 260 kHz or 125 MHz signals/noise. Does this noise happen when no audio is played, and at all times?

Justin

Audio

Audio forum

PCM1794A Noise@260kHz and 125MHz