Noise on VIN

ATmega328p Controller /w pluggable connectors for 6 constant current LED drivers with PWM control
rpu_bus
Posts: 207
Joined: Sun Sep 18, 2016 6:07 pm

Noise on VIN

Postby rpu_bus » Mon Jan 01, 2018 2:21 pm

RPUlux is going to have a lot of noise on VIN, with six switch mode, LED drivers that are being PWM'd it is going to be nasty. The SMPS that drops VIN down to 5V should keep that mostly away from the MCU. I have a Tantalum capacitor on the 5V which has an ESR that can dissipate power from resonance in the supply, and it also has several 0.1uF bypass capacitors at good locations to shift the resonance into the Tantalums power dissipating sweet spot. These are common techniques but I guess I wanted to comment on them.

I did not put a Tantalum on the VIN because I don't think I care about the noise there. Actually, it will most likely be powered from a source that has an ESR (e.g. battery) or a Tantalum at its output, but if something fails to work then I may have to change my mind.

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