Technical Articles

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Designing Power for Sensitive Circuits

Low power, high performance circuits are often plagued by power supply related issues.  This common occurrence is frequently due to mythical (or misapplied) rules-of-thumb.  These rules of thumb often lead us in the wrong direction, making things worse rather than better.  In this article, I’ll highlight some of the most common mistakes engineers make and share some fundamental rules for designing clean power for sensitive circuits.  Applying these rules will result in higher performance, lower cost designs with fewer design iterations.


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BER- and COM-Way of Channel-Compliance Evaluation: What are the Sources of Differences?

We analyze the computational procedure specified for Channel Operation Margin (COM) and compare it to traditional statistical eye/BER analysis. There are a number of differences between the two approaches, ranging from how they perform channel characterization, to how they consider Tx and Rx noise and apply termination, to the differences between numerical procedures employed to convert given jitter and crosstalk responses into the vertical distribution characterizing eye diagrams and BER. We show that depending on the channel COM may potentially overestimate the effect of crosstalk and, depending on a number of factors, over- or underestimate the effect of transmit jitter, especially when the channel operates at the rate limits. We propose a modification to the COM procedure that eliminates these problems without considerable work increase.


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