How do I calculate the size of a filter capacitor to reduce the ripple when I have a microcontroller on the same regulated power supply as a high current load like an LCD strip or a motor controller? (I'm aware of the need to use flyback diodes on inductive loads.)
If I'm building a power supply that rectifies AC and filters it, there are lots of articles out there that describe how to calculate the size of the filter capacitor, e.g.: https://makingcircuits.com/blog/calculate-filter-capacitor-smoothing-ripple/
The formula for that is
C = I / 2 x f x Vpp, where
I is the load current,
f is the AC frequency (usually 50 Hz or 60 Hz, and
Vpp is the allowable ripple.
All the searches I've done lead me to articles about filtering ripple on AC power supplies.
However, I'm not trying to smooth ripple from a rectified AC supply. I'm trying to smooth out variations in an already regulated 5V supply as the load to the supply changes.
Say, for example, I have a regulated 2A 5V supply that's driving a 1.5A LED array AND an Arduino-based system that draws ≈200mA. I am feeding the 5V from the supply into the Arduino, and also using it to drive the LED array. I'm under the 2A limit of the regulated supply, with a little "wiggle room", but concerned that as the LED array turns on and off, it will cause droops and spikes in the regulated 5V supply as the power supply lags slightly in adjusting the output voltage for changes in load.
Assume the Arduino can tolerate ±0.5V on it's 5V supply. I imagine the LED array's load spikes are going to be nearly instantaneous, like switching on and off a resistive load. (Assume the 5V supply is a typical switching supply. I don't know how to estimate its max voltage variation under changing load, or recovery time, and need help with that bit.)
How do I calculate the rating of a filter capacitor to put on the 5V rail that feeds the Arduino to smooth its input voltage as the load to the power supply changes?