Phil Anderson wrote:
>
>I have a clock with CMOS output running around a pc board, roughly 8
>inches, to the XTAL input of a PIC. The clock is 16 Mhz, and while scoping
>it, I see that it rings badly, i.e. large overshoot on the rising edge and
>large undershoot on the falling edge. Spectrum analyzer picks it right up!
>Nice 16 Mhz picket fence.
>
>How may I clean up this ringing?
>

First, make sure the scope gnd lead is as short as possible,
and placed as close as possible to the point[s] being tested.
Otherwise, you get loads of ringing.

Second, for something simple, try a 30-47 ohm series resistor
between the CMOS output pin and the driven line --> "source-series
termination".

- danM

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