I have an 8-LED array driven by an 8-channel source driver (TD62783AP) controlled from an 8-bit shift register (74HC4094).
When it comes to dimming the LEDs using PWM, I came up with two solutions, and I was wondering if one was better than the other:
- I can PWM the Output Enable pin of the shift register
- I can PWM the supply VCC of the source driver
Which one, if any, would be best, and why ?
Best Answer
I would say you should apply the PWM signal to the OE pin of the shift register because the driver is not designed to have a voltage level at the inputs higher than the supply voltage due to the clamp diodes at the input.