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Atta Rehman , 08-22-2025, 03:29 PM

I have designed 16 channel ADC (ADS1299) interfaced with ESP32S3 transmit data over Wi-Fi application for EEG/EMG.
1. Design version 1.0 works well, as I plotted PSD of 16 channels in figure below. (PCB size 4X3 inches)

2. Next design requirement is to minimize size of PCB. Down to 3x2 inches. I have designed board with same specs just with small form factor. PSD of 16 channels has noise 9.76Hz peaks as shown in figure below.


 During debugging noise reason, I track down reason, when I increase Wi-Fi signal transmission strength 19dB, same 9.76Hz voltage sag of 130 mV observed at 3.3Volt as shown in figure below. By Decreasing Wi-Fi strength in firmware down 13dB/ 8dB voltage sag & noise decreased.



 Total board is operating on Li-ion battery 3.7V with LDO ( TLV75733) , and board current consumption 200mA.
 Please suggest how I can resolve this issue of power noise link with Wi-Fi signal strength.

Question: What will be possible reason of this noise?
Either is it placement issue as ADS1299 placed near to Wi-Fi ESP32S3 antenna field?
Please suggest, what is route cause of this issue either EMC/ EMI or something else?
What type of Faradays cage / shielding is required around ADS1299 to secure analog section from 2.4 GHz Wi-Fi interference?
Power dip of 130mV is either due to load current supply limitation, but I am using same LDOs, which was used in design version 1.0.
Now I am designing 64-channel ADC board with (8XADS1299) and ESP32 transmit data over Wi-Fi.

1. Should I used modular approach i.e. Digital PCB with ESP32 and other digital peripherals and Analog PCB with 8 ADC's?
2. How isolate Ground DGND & AGND?





Figure : :Power supply Scheme of PCB.








PCB BOARD Version 2 is 6 LAYER. (Each layer as shown in figure)

Atta Rehman , 08-22-2025, 03:52 PM