Very sensitive Mixed signal PCB. EEG (Brain wave sensor). 0.010mv sensitivity

I have seen multiple examples of EEG PCB's where they have a MCU and a separate RF module.

Considering the fact that the RF module (MDBT53) is literally a NRF5340 with an antenna, should I just use that to process everything

The Primary MCU is also a NRF5340

I believe the reason they have two separate ones if to reduce noise and to split the Bluetooth transmission internal noise from the primary MCU

ADS1299 is the big ic on top layer that does all the ADC. The microcontroller is for processing the data.

 

Your already know the answer, split the duties between controllers like any (IMO) sane designer would do. The design decisions for sensitive analog/process and good RF often conflict. The RF co-processor concept is a very sound one.

 

Your already know the answer, split the duties between controllers like any (IMO) sane designer would do. The design decisions for sensitive analog/process and good RF often conflict. The RF co-processor concept is a very sound one.

Yea based on the fact that every single other pcb design has it like that I'm sure its the right answer but you never know I am using newer better ic's

 

The reason your PCB has two NRF5340s (MCU + RF module) is to reduce noise coupling from RF and high-speed logic into the EEG analog path.
So, even though the MDBT53 can act as your main MCU, for EEG-level precision, it’s wiser to use one nRF5340 (or another low-noise MCU) near the ADS1299 for data capture and preprocessing. And use a second isolated nRF5340 (MDBT53) purely for wireless transmission.

 

The reason your PCB has two NRF5340s (MCU + RF module) is to reduce noise coupling from RF and high-speed logic into the EEG analog path.
So, even though the MDBT53 can act as your main MCU, for EEG-level precision, it’s wiser to use one nRF5340 (or another low-noise MCU) near the ADS1299 for data capture and preprocessing. And use a second isolated nRF5340 (MDBT53) purely for wireless transmission.

could you please explain in a little more detail exactly why? Like for example... where is the noise that the rf module generates affecting the circuit? is it in the power rail, the spi? Is it because its farther away from the ads 1299? does it have something to do with the di on the nrf ic? does it matter that the nrf5340 is a newer ic that has dual cores could that potentially make a difference?

 

No, you're thinking like a programmer, not a hardware designer that has a basic understanding electrical of science.

Your application has several physical requirements.
One EM requirement, RF Chip, needs EM field emissions not to be impeded for good communications. Another EM requirement, EEG signal chip, is for EM field suppression for good source signal fidelity.

Just thinking about doing both, on one chip, in a sensitive signal application.

 

No, you're thinking like a programmer, not a hardware designer that has a basic understanding electrical of science.

Your application has several physical requirements.
One EM requirement, RF Chip, needs EM field emissions not to be impeded for good communications. Another EM requirement, EEG signal chip, is for EM field suppression for good source signal fidelity.

Just thinking about doing both, on one chip, in a sensitive signal application.

Well it turns out your wrong. I actually can use just the rf module by itself.

 

Well it turns out your wrong. I actually can use just the rf module by itself.

Talking like a programmer again.

Nobody said you couldn't just use (program the functionality) the RF modules by itself, we just think it's an unwise optimization.
I guess all the other designs with split modules were created by fools that didn't know about two core modules.

 

Talking like a programmer again.

Nobody said you couldn't just use (program the functionality) the RF modules by itself, we just think it's an unwise optimization.
I guess all the other designs with split modules were created by fools that didn't know about two core modules.

You keep saying im thinking like a programmer but the original comment that you replied that to, is literally pure electrical engineering related questions. Not a single one has anything to do with programming, not even the thought process.