Datasheet

Application Report
SZZA016B - June 2001
7–231
Basic Design Considerations for Backplanes
Shankar Balasubramaniam, Ramzi Ammar,
Ernest Cox, Steve Blozis, and Jose M. Soltero
Standard Linear & Logic
ABSTRACT
This application report describes design issues relevant to the parallel backplanes typically
used in the wireless, datacom, telecom, and networking markets. Designing a
high-performance backplane is extremely complex, because issues such as distributed
capacitance, stub lengths, noise margin, rise time (slew rate), flight time, and propagation
delay must be defined and optimized to achieve good signal integrity along the
transmission line.
This application report uses a GTLP backplane driver to study the effects of these factors in
an actual backplane application. Guidelines that enable the design engineer to successfully
design a high-performance backplane with GTLP or other single-ended open-drain devices,
such as BTL, are provided.
This application report is a revision of the original
Basic Design Considerations for
Backplanes
, literature number SZZA016, published June 1999. The theory text was rewritten
to make it clearer, and the theory-to-practice section was added, based on work done with
the GTLP evaluation module (EVM).
Contents
Introduction 7–233. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Backplane Design Topology – Point-to-Point vs Multipoint 7–233. . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Distributed Capacitance 7–235. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Optimum Termination Simulation 7–239. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Stripline vs Microstrip Tradeoffs 7–240. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Backplane DC Effects 7–241. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Effect of Changing Stub Length on Backplane Signal Characteristics 7–242. . . . . . . . . . . . . . . . . . .
Distributed Capacitance – Theory to Practice 7–245. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Fully Loaded Backplane 7–246. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Lightly Loaded Backplane 7–247. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Very Lightly Loaded Backplane 7–249. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Backplane DC Effects – Theory to Practice 7–252. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Conclusion 7–253. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Bibliography 7–254. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Glossary 7–254. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .