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Sink current using PCA9685?


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Hi, all
I'm using a PCA9685 with a pinout board like Adafruit's. I'm trying to run a bunch of LEDs at 20 mA, and the chip is supposed to be able to source 10 mA and sink 25 mA. I understand that to have it Source, you connect the LED between the PWM and GND pins and to Sink you connect it between V+ and PWM. 
I've tried both ways and using a multimeter and a red LED I get 12.5 mA. Why is it not 25 in Sink? Also, why do I get 12.5 on Source mode as well?
Is there anyone have ideas of it? if possible a simple explanation would be nice. Many thanks.☺️

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That is a complex beast! Given: "Each LED output can be off or on (no PWM control), or set at its individual PWM controller value. 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."

If you are using the PWM control the meter would not show the peak currents to the LEDs. Other then that it is difficult to help troubleshoot something that requires programming.

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  • 4 months later...

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