I want to use the PAM2861 LED driver.
It can handle my intended load (1 A and two LEDs around 3 V per channel) and I know this because someone with a similar project used it. It's also available at JLCPCB which means I can get it assembled for me and still save money (not to mention the equipment I'd need to buy for reflowing correctly).
Problem with it is that the PWM frequency and resolution are limited. I want a better resolution and a higher frequency, but I can't find anything else in their catalog that will do.
Why not just use an N-FET inserted after the LED string and drive that FET with low-passed PWM from my Arduino? The low-pass also eliminates the flicker that comes with PWM (this is annoying if I want to use a camera anywhere near the thing). Here is a schematic:
As far as I can tell, looking at the typical application example and the block diagram (when I say look, I am still a newbie), I can't see this being problematic, but maybe it is.
Am I right to think all this would do is add more resistance to the string as the PWM duty cycle is lowered? Does this interfere with accurate voltage regulation/constant current switching?