DesignCon 2022 Schedule Builder

Serdes receivers have evolved into multi-faceted devices capable of identifying NRZ and PAM4 logic symbols from closed eye diagrams. As receiver complexity has increased, so have stressed receiver tolerance techniques that test receivers with worst-case but compliant test signals. Specifications define worst-case signals in terms of eye width (EW) and eye height (EH) at the receiver. The prescribed eye closure, defined with respect to symbol error ratio (SER), is achieved by subjecting test signals to the frequency response of a specified interconnect and adding jitter, noise, interference, and crosstalk. Since EH and EW depend on the signal impairments in different ways, calibrating the stress signal is an optimization problem of two simultaneous functions (EH and EW) of common variables (the signal impairments ). Our presentation begins with a brief but complete review of signal impairments and how they simultaneously affect EH and EW. We then introduce COM (channel operating margin) to help simplify generation of the stressed signal, but at the expense of introducing yet another optimization problem. We conclude by discussing future challenges in receiver testing for more complex PAM signaling schemes as well as schemes generalizing the concept of differential signaling, like MIPI-C-PHY, ENRZ or CNRZ-5.

Takeaway

We hope to give you an insight about challenges with eye measurements at current and evolving technologies.