Robert Bailey

ADC crosstalk when input exceeds ref/rail

Discussion created by Robert Bailey on Feb 27, 2006
Latest reply on Feb 27, 2006 by Robert Bailey
With previous projects (HC11)when the input exceeded the positive supply, there were no issues as long as there was decent (10k) series impedance.

Curently I am designing with an HC908AP64 and am getting a lot of crosstalk issues, and the impedance limiting trick is not working.

Even the "resistor....diode to +5....resistor.....input" circuit is not effective.

Is there some trick in software to eliminate the crosstalk (I am using
Codewarrior) or some whiz-bang circuit trick? Generally the signals will be 0-5 volts, but I can't guarantee that......

Any ideas guys.....?

(I tried to search the board and freegeeks and found nothing....)