While designing the RF Frontend board, we ran into a VAPC pin we had no idea about. This document will explain its purpose and where we go from here.

APC translates to Analog Power Control, which means, you’re using analog signals to control power. Usually, the chip requires some sort of signal to even turn on in the first place. It’ll have some threshold value where it’s considered LOW and some value where it's considered HIGH. Any LOW input signals will just result in the chip turning off. Any HIGH signals result in the chip functioning and outputting something.

From there, you have to change the voltage of the inputted signal (the V in VAPC) to change the output power. For example, 1V may result in an output of 3 dB, while 5V may result in 16 dB.

Additionally, VAPC pins need a minimum current to be considered “HIGH”. Usually, this is relatively small, and all that matters is it’s above the minimum; changing the current past usually wont affect the output power.