Hi,
I have notived in several PHY designs that the termination impedance is 50ohms. But there are usually digital bits to tune them.
How does the tuning happen in production ICS?
I guess they can't characterize each chip......


Thanks in advance

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They do for both TX and RX. All standards has limit on S11,S22..very difficult to meet if you don't have some kind of calibration. Not only from S11,S22 point of view but also from TX driver swing and current point of view also termination is imp...
Some people does this with a tester burning E-fuse which saves some initial bring up time.

Raj!