Datasheet
Application Report
SCBA015A - March 2001
7–3
Fast GTLP Backplanes With the GTLPH1655
Peter Forstner and Johannes Huchzermeier Standard Linear & Logic
ABSTRACT
This revision of the
Fast GTL Backplanes With the GTL1655
application report addresses
improvements, such as the improved OEC circuitry and implementation of the
Texas Instruments TI-OPC circuitry, that have been incorporated in the GTLPH1655
device. These improvements significantly improve signal integrity in distributed loads.
This application report describes the physical principles of fast bus systems and the problems
that can arise in their development. These descriptions are based on line theory, and various
specifications of TTL, backplane transceiver logic (BTL), Gunning transceiver logic (GTL),
and Gunning transceiver logic plus (GTLP) integrated circuits are compared.
In addition, this application report presents the performance of the SN74GTLPH1655. This
new UBT device
provides an optimum solution for the design of backplanes for future
high-speed bus systems.
Comprehensive measurement results of the SN74GTLPH1655 also are included in this
application report.
Contents
Introduction 7–6. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Physical Principles 7–7. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Does a Line Behave Like a Capacitive Load? 7–7. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Transmission-Line Theory in Practice 7–9. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Effects on Bus Lines 7–13. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Beginning of the Line: The Incident Wave 7–13. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
End of the Line: The Reflected Wave 7–15. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
New Bus Systems Are Needed 7–17. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
BTL Bus 7–18. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
GTL Bus 7–19. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Comparison Between BTL and GTL 7–20. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
New Backplane Solution: SN74GTLPH1655 From TI 7–21. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
OEC, TI-OPC, and UBT are trademarks of Texas Instruments.