Teledyne LeCroy Eye Doctor II - Manual (Page 36)

Eye Doctor II Software
Case 2
A C LOSED E YE (6G B / S T HROUGH 30” O F FR4)
With no equalization applied, this signal clearly shows a closed eye. However, we cannot yet say the sig-
nal truly does have a closed eye because we cannot correctly recover the clock from the signal. There-
fore, we must feed a reasonable signal into Clock Recovery.
The following screen-shot shows both EDrIn and EDrEqu traces having the same signal, because no equal-
ization was applied. The output of EDrEqu is reframed, meaning it is displayed on a different scale.
Case 2, without equalization
If we go to Eye Doctor II's Clock Recovery dialog and touch Find Frequency, a clearly incorrect result (in
this case, 9.04878Gb/s instead of nominally 6Gb/s) is produced. If we Show the recovered clock (Show on
the Clock Recovery dialog) we can see it is missing some edges. The issue is, of course, that we need to
feed a reasonable signal (one forming an open eye) into the Clock Recovery. As follows, we use the CTLE
to equalize the signal, change the data path so CTLE is only used on the path to Clock Recovery, and then
only use DFE to equalize the signal for EyeDrOut.
Note: We have entered the nominal bit rate, 6Gb/s, manually.
First, we can set up the CTLE by adjusting the Boost until the signal appears equalized. It just takes a few
seconds to determine that 8dB looks good:
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