Honored ContributorHi
Can someone explain to me why the voltage overshoot of Max V is so high? and how to improve this voltage overshoot ? Here is an example I captured from an oscilloscope. In this case the undershoot of rising edge and overshoot of falling edge are almost at the same voltage level. http://www.alteraforum.com/forum/attachment.php?attachmentid=12389&stc=1 Thanks. Bien
Honored ContributorHi,
how are you probing this? The screenshot looks like a typical case of probe-induced ringing. If you have a second, equal probe, connect the second probe to the same point. The measured signal must not change, otherwise you know your probe load is too high, and you'll need a probe with less load (e.g. an active one). Then it could be ringing due to impedance mismatch. This should only be a problem if the signal propagates through a long trace. However, maybe some termination would help, even if it's not perfectly matched (if I decipher your tiny screenshot correctly, the signal has only 10 MBit/s). The simplest termination would be to add an e.g. 50 Ohm series resistor near the Tx end. Best regards, GooGooClusterHonored ContributorIt looks the the ground wire on your oscilloscope probe is either disconnected, or too long.
Honored ContributorHi
I made a simple 50 Ohm termination as you suggested and the voltage overshoot becomes much better. Thank alot GooGooCluster.Honored Contributor
