Noise on ADAU1701

looks like the return line for you decoupling caps do the long way around.

Better use a 4 layer board and do 1 layer ground with nothing else on it. and put vias directly next to the decoupling capacitors.

Benno

Benno's advice for a four layer board will result in less headaches and more quiet. For our first -1701 design we got away with two layers -- yet this was a telephone application where noise wasn't of particular concern. We switched to four layers for later designs.

The initial measurements on our mixer prototype were disappointing. We then found that two noise sources external to the mixer's ADAU1701s had affected the result. The first, switching noise from the 3.3V converter, was fixed by going to a MHz converter. We also had to deal with noise injected by multiplexed front panel LEDs in the system.

Best regards,

Bob

Thanks for your advice- I want to avoid 4 layers if possible due to cost sensitivity- the only noise i have is on the 2 analogue ins of the DSP- I have 4 other audios going in through cypress ADCs and they are quiet as

Hello Anthony,

I strongly recommend you use four layers. In today's PCB world it is not very expensive to go from two to four layers.

Then follow the advice about how to connect decoupling caps on the power rails that is in the ADAU1452 datasheet. In the PCB Considerations section.

Dave T

I normally use JLC for 4 layer boards, it takes 2 days longer than 2 layer boards and for about $28 you have 5 boards on your desk 2 weeks.
Last couple of times I let them also put the 0402 capacitors and resistors on the pcb.

Benno

thanks for the tip