I'm looking for some advice on how I might protect an electret mic amplifier from picking up noise from 25mA current bursts that will be happening on the same power rail.
My setup involves 3 major components:
- ATTiny1614 mcu
- W25Q32JV flash IC
- Electret mic w/MAX6644 amp (schematic)
The issue is that whenever I execute a write command to the W25Q32JV module, the temporary higher current draw (~25mA) is being picked up and amplified by the electret mic amp, creating a noticeable "tick" in the mic output.
I've tried adding various bypass caps (0.1u - 100uF) at the VCC/GND pins of each of the components, but it hasn't created a noticeable difference. The mcu only has a single GND pin (no AGND) unfortunately.
Using a separate power supply for the W25Q32JV and the mic/amp isn't an option, although in testing this does significantly improve the mic output.
Does anyone have any suggestions (general or specific) that I might consider?
I'm happy to provide a detailed schematic if it would be helpful, but it's basically just the 3 components listed above with a 0.1uF bypass cap on the ATTiny.
[EDIT 1/1/20] Thanks for the comments everyone!
@Brian Drummond do you mean placing a low pass RC filter on the VCC input of the mic/preamp board? Do you have any recommendations for RC values to try?
@skvery the flash writes need to occur at the same time as the mic input unfortunately.
@JRE I am using the Adafruit module for the time being. Just using breakouts I have around but I'll be putting together a custom PCB soon.
@Drew agreed, although I'm trying to keep the cost really low so this might not be an option. Just out of curiosity, I tried powering from another 3.3v source I have that uses a AP2112-3.3 and it produced less noise. I may have to play around with a few different regulators.
@Andy aka are you referring to the two 1K resistors (R1, R2) pulling up the mic output?