PCM4202: high noise in quad Rate Mode

?? ?

Part Number: PCM4202

PCM4202 works in the PCM Slave Mode Operation or PCM master Mode Operation. I found that quad Rate Mode (LRCK=200KHz,SCKI= 128FS,BCK= 64FS) had high noise, while other modes had low noise.Figure 1 shows the corresponding FFT diagram.

over 3 years ago

0 Jeff McPherson over 3 years ago

TI__Mastermind 40285 points

Hi,

Are you changing sampling modes while keeping power on? Sometimes changing sample rates can cause noise issues without a proper power cycle. Also can you share a schematic of your setup?

Thank you,

Jeff

0 ?? ? over 3 years ago in reply to Jeff McPherson

Prodigy 10 points

hi,jeff!
We tried the following two methods, but none of them worked.

1. Set the sampling mode before power on.

2. After changing the sampling mode, apply a low level to the RST pin for more than 65536 system clock cycles to force the PCM4202 to enter the power-down state.Then apply a high level to the RST pin.

0 Sanjay Dixit over 3 years ago in reply to ?? ?

TI__Mastermind 23030 points

What are the timings sent into the chip? For example with fs=192khx the Sclk is 36.6Mhz.Is there a 22 ohm series resistor in series with the clock near the source? Sometimes clock reflections can cause improper function.

0 ?? ? over 3 years ago in reply to Sanjay Dixit

Prodigy 10 points

hi，sanjay ！

We have changed the series resistor in series with the clock near the source from 100Ω to 22Ω。And the timings sent into the chip is as follows : SCLK=25Mhz BCK=SCLK/2 LRCK=BCK/64 （V_cc=5.0V, V_DD=3.0V,）. The noise is still there.

Regards！