I#M working on a 24channel LED Dimmer with up to a couple Amps per Channel an 12-24V.
For PWM generation I use PCA9685 I2C Controller.
I have now my prototype PCB with 2 PCA on it.
While I measure 0V at one PCA9685 channels when they are “off”, I measure 0.5V at the other PCA9685.
When they are on, everythings fine with 5V.
I added a 10k Pulldown, but that didn’t solve it. Voltage only Down to 0,3V.
I configured both PCA to Totem Pole (which is the default).
“The LED output driver is programmed to be either open-drain with a 25 mA current sink capability at 5 V or totem pole with a 25mA sink, 10 mA source capability at 5 V.”
But also with Open Drain there is no difference.
I checke with my breadboard test setup where I used breakouts for PCA9685 and there I also measure 0.5V when the channels are off.
I cannot explain the difference on my PCB (for reference see attachment).
But I can also not explain why there are 0.5V when off…
I don’t know if this causes problems, for now I’m just confused and curious.
KRS-XL_DIM-24CVLED.schematic.pdf (141 KB)