Forum Discussion

Altera_Forum's avatar
Altera_Forum
Icon for Honored Contributor rankHonored Contributor
10 years ago

Max V: Voltage overshoot is too high ?

Hi 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 under...
Altera_Forum's avatar
Altera_Forum
Icon for Honored Contributor rankHonored Contributor
10 years ago

Hi,

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,

GooGooCluster