I have issues with my FPV camera. My camera is a RunCam split 2S (concept is similar to Caddx turtle).
This camera turns off almost instantly after I have plugged in my battery. When I probe the voltage between 5V and ground, I can see the voltage drop from 4.9V to 4.6V as soon as the camera starts recording (which it does automatically when powering it). Then, when the camera shuts completely off, the voltage goes up again. Also, I can press a button and the camera will turn on but also back off again
Hooking up a phone charger to the camera gets the voltage up again (and makes the camera run stably), but I obviously don't want to fly around with a power bank attached to my drone.
Unfortunately, the VTX is also wired to the flight controller's 5V converter instead of its own.
TL;DR: The issue is not that the voltage has too much ripple. The issue is that the voltage converter on my FC is not strong enough.
Would a capacitor at the input (XT60 connector) make any sense? If yes, which size should it be? I have 220µF and 1000µF electrolytic caps.
short answer for future people: additional, external voltage converter/BEC; use all available voltage converters (VTX, FC, (PDB)); do not make them parallel!
long answer: see accepted answer