SN74VMEH22501: ringing in simulation

Hi Michael,

It's likely you're experiencing some transmission line-like effects while using this part, which means that impedance matching your outputs & inputs is very important for signal integrity. The outputs of this device have quite a high drive strength, so this can be a real issue if not handled properly.

Thanks!

Chad Crosby

We have a simulation that shows that the ringing downstream gets reduced when we put 10 ohms on the output of the driver.  However what happens to the received signal when that same 10 ohm resistor is on the input because that could cause another reflection?

Also, do you know anyone else that had to do this to get this xcvr to work correctly?  This is not covered in the data sheet.

Hi Michael,

We have an FAQ about logic devices driving transmission lines that looks to be very useful for this situation. See the below:

[FAQ] What happens when I connect a logic device's output to a 50 ohm transmission line?

I'd recommend removing the 10 Ohm resistor on the receiving end, and just trying to increase the resistance on the output until you see improvement here. If you have any design files (i.e. a schematic and/or layout) and scope shots to share with me, that would greatly help me help you.

Thanks!

Chad Crosby

Taken offline for further detail.