I'd like to put a pump drive circuit similar to the one shown below on the same PCB that has two I2C devices, a GPS module, seven analog signals, an ESP32 MCU transmitting WiFi via a trace antenna, and a SPI bus with a microSD card and flash.

I'm worried about signal interference with all the switching going on (the pump is driven with PWM at the MOSFET). Is there a way to mitigate this by simply separating the circuits to different regions of the board, or using an RF shield? If it's the latter, where would I put the shield? Over the microcontroller? Over the pump drive switching components?

I don't mind putting it on a different PCB but if there's a way around it I'd prefer to have it all on one board.

Pump Drive Schematic

  • 1
    \$\begingroup\$ The EMI would be both conducted AND radiated so a Faraday shield is not enough. \$\endgroup\$ – Sunnyskyguy EE75 Jun 25 at 4:41
  • \$\begingroup\$ How often do you switch the pump? \$\endgroup\$ – Voltage Spike Jun 25 at 6:12
  • \$\begingroup\$ If you can separate your pump power & ground from your control circuit power & ground consider using an opto-coupler to drive the MOSFET gate. This would at least solve potential issues with conducted noise. \$\endgroup\$ – Nedd Jun 25 at 9:25
  • \$\begingroup\$ So you have a 12 volt battery being switched, and you want a 12 nanovolt radio to function, on the same PCB, albeit at different frequencies. Do you understand how to create "local batteries" to supply charges locally? using small resistors in the VDD lines, and large capacitors shunting VDD, over a Ground plane? \$\endgroup\$ – analogsystemsrf Jun 25 at 10:34
  • \$\begingroup\$ @laptop2d Turning on the pump for half an hour every 4-6 hours. \$\endgroup\$ – YNGVV Jun 27 at 1:48

If your worried about the pump PWM generating frequencies in the 2.4GHz range then short the currents out on the board by using low impedance caps (low ESR and ESL).

enter image description here

X2Y caps are a good option, they have a lower impedance than regular caps because they have two terminals that halves the ESL. Lower ESL means higher performance at high frequencies.

enter image description here
Source: https://www.farnell.com/datasheets/2046090.pdf


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