RPLaJeunesse
- Joined Jul 29, 2018
- 252
500K is exceedingly high, and could make the circuit sensitive to noise and stray path leakage. I consider 47K a high number, and would prefer to see more like 10K. Given a 12V LED load and a DMC3021 safe max of 7.1A steady state at turnoff you possibly would hit maybe 3V at 3.5A max, from the DMC3021 curve for SOA (fig. 11) the part will survive an over 10ms turnoff. But that is one pulse at 25C case and 125C chip temp rise. Your case temp will be higher, the allowable rise lower, and repetitive pulsing. I'd apply a safety factor of 10x and stay below 1ms turnoff. Using 47K meets this comfortably.
Side note: If you are PWM dimming (and you didn't say you were) I've learned 15Hz is very flickery, 48Hz is tolerable in a dark, stationary environment, and 100Hz+ is called for if there is motion between LED and viewer. AT 100Hz a 1ms turnoff is too long, more like 100us maximum. Using 10K resistors should be fine for this speed.
Side note: If you are PWM dimming (and you didn't say you were) I've learned 15Hz is very flickery, 48Hz is tolerable in a dark, stationary environment, and 100Hz+ is called for if there is motion between LED and viewer. AT 100Hz a 1ms turnoff is too long, more like 100us maximum. Using 10K resistors should be fine for this speed.