I was about to pull the trigger to buy several of these boards until I noticed in the schematic that there’s a 10 kΩ resistor on the EN pin of the regulator. Won’t this draw a constant current of 0.42 mA at 4.2V (LiPo)?
I’ve found that the majority of SparkFun boards either don’t use a resistor on the AP2112 or use a much higher impedance of 100 - 220 kΩ. I’m curious to know why 10 kΩ was used instead.
It’s going to pull some current, but keep in mind that it’s 10K to EN and not 10K to ground. It’s just a pullup, current draw is probably in the microamp range and it’s going to be insignificant compared to what the rest of the board is drawing.
Don’t know for sure why 10K was chosen, 100K would probably work just as well too.
What threw me off is the fact that the EN pin isn’t actually tied to a microcontroller GPIO. It’s only broken out to the 0.1” header pin. It makes total sense that it’s only going to draw current when disabling the regulator. The impedance of the EN pin is 3 MOhm so no worries there.
I agree that a 100 kOhm resistor would have ask been a good choice (1/10th the current draw).
