System level approach for assessing and mitigating differential skew for 10+ Gbps SerDes applications

Abstract

Weave-induced skew on printed wiring boards (PWB) for 10+ Gbps SerDes data rates can be very significant. In this paper, we not only investigate weave-induced skew but also look at other sources of skew. We show the weave skew results taken from measurements of three different test boards. Results from a fourth board are presented to examine PWB differential via skew. Measurements from a fifth board are analyzed to determine total channel skew. We propose a budget such that a certain amount of skew can be tolerated with a small increase in channel insertion loss. We then present a case study to project overall performance on PWB yield. We observe a number of anomalies with our test results and suggest additional studies to guard against unpredicted high skew.