Hi group: The problem I initially had on using the A/D on the ATmega128 was that I am holding an A/D input at steady state and am changing all other 7 channels in small increments until they reached the max level then they would start from ground again. The problem I initially had on using the A/D on the ATmega128 was that the steady state input would start to drift higher (i am using hyperterminal and software to see the output) for a certain range of inputs on the other A/D inputs. This problem got traced back to a dipping AVcc. The power supply to AVcc is a shunt reference(LM4040AIM3-5.0) with a 590 ohm series resistor. I changed this resistor to 200 ohm and the problem went away. It should be noted that AVcc and AVref are tied together and was initially designed for an ATmega103. I know the current draw for AVref, but cannot find the Maximum current draw for AVcc. Does anyone know where or how to find this? Thanks Draper
Message
ATmega128 using A/D with AVcc and AVref tied together - max current draw?
2012-03-27 by Draper