ADAU1701 integrated ADC has p-p100mV High freq Noise
I used ADAU1701MINIZ EVM board, and also another adau1701 board bought from alibaba as well as self-designed board, in integrated ADC connected with integrated DAC case, I see 100mV p-p noise in DAC output pin. the noise frequency ranges from 5khz-3MHZ. (direct connect ADC and DAC in software setting)
I use external PCM1798 ADC and connect with internal DAC, noise disappear. When use external DAC and internal ADC, the noise is still high.
power supply ripple is lower than 5mv, I changed the capacitor of CM FILTA FILTD to 220uf 90m ohm electrolytic capacitor,the noise is still high.
the input of ADC is connected with a 18k resistor and a 22uf capacitor, then short to GND,but noise is still high. changing 18k resistor to 8k does not change the noise level (still 100mv p-p).
is this because of crosstalk of dvcc and avcc?
need your help.
Thread Notes
Harishgowtham - Moved from Processors and DSP to SigmaDSP Processors & SigmaStudio Dev. Tool. Post date updated from Friday, March 1, 2024 8:42 AM UTC to Monday, March 4, 2024 5:02 AM UTC to reflect the move.
Harishgowtham - Moved from Processors and DSP to SigmaDSP Processors & SigmaStudio Dev. Tool. Post date updated from Monday, March 4, 2024 5:02 AM UTC to Monday, March 4, 2024 5:02 AM UTC to reflect the move.
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Hello Louie.Li,
What I do not understand is how you can get up to 3MHz of noise when the ADC is running at I presume 48kHz?
How are you measuring the noise? Are you using an oscilloscope or a DVM?
Supply some screenshots. that might help. You may be picking up the noise from some other source.
Louie.LI said:
the input of ADC is connected with a 18k resistor and a 22uf capacitor, then short to GND,but noise is still high. changing 18k resistor to 8k does not change the noise level (still 100mv p-p).
Can you draw what you did here?
Did you try just shorting the input to ground at the jack?
The other part of the problem here is that most likely you are powering this up via USB and some USB power and ground is not well implemented.
Dave T
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