PIC ADC - Current Limiting Resistor Req'd?

Thread Starter


Joined Jul 30, 2009
I'm just using a PIC to read a voltage divider will give readings between 0 and 5 volts. Do I need a current limiting resistor before it hits the ADC pin on my PIC?


Joined Dec 3, 2009
What values are you using in your current divider? I never have used a current limiting resistor on the ADC inputs and have had no problems.

Thread Starter


Joined Jul 30, 2009
I have a 1k on the 5 volt side and a 20k potentiometer on the other. Ranging from ~500ohms to 20k.

5v >> 1k ohm : ADC pin on PIC : 0~20k ohm >> 0 (GND)
Last edited:


Joined Apr 20, 2004
To need a voltage divider, you must have a voltage to measure that exceeds the range of the ADC. As long as the divider does not load the input signal and distort it, it should work.

What is the amplitude of your input?


Joined Sep 7, 2009
There is no need to use a resistor if you are within the voltage specifications, in fact it could cause accuracy problems if you used a high value.
From 12F629 datasheet:
The maximum recommended impedance for analog sources is 10 kΩ. This is required to meet the pin
leakage specification.