Datasheet
SZZA016B
7–254
Basic Design Considerations for Backplanes
Bibliography
Higgs, Mike, 1997.
Advanced Schottky Load Management
, Texas Instruments application report,
SDYA016.
Ammar, Ramzi, 1997.
GTL/BTL: A Low-Swing Solution for High-Speed Digital Logic
,
Texas Instruments application report, SCEA003A.
Johnson, Howard, and Graham, Martin, 1993.
High-Speed Digital Design
, Prentice-Hall, Inc.
Glossary
C
io
Input/output capacitance of the transceiver
C
o
Characteristic capacitance – capacitance per unit length of a transmission line
in free space
GTL Gunning transceiver logic– operates at signal levels of V
TT
= 1.2 V, V
REF
= 0.8 V,
and V
OL
= 0.4 V. GTL+ is a derivative of GTL that operates at higher noise-margin
signal levels of V
TT
= 1.5 V, V
REF
= 1 V, and V
OL
= 0.55 V, and moves V
REF
from
the normal ground-bounce area.
GTLP Gunning transceiver logic plus – normally associated with slower edge-rate devices
optimized for distributed loads that allow higher-frequency operation in heavily loaded
backplane applications
L
o
Characteristic inductance – inductance per unit length of a transmission line
in free space
R
TT
Termination resistance – resistance used to match the effective impedance of a
transmission line in order to minimize reflections. R
TT
= Z
o(eff)
t
(flight)
Flight time – time it takes a signal to propagate between two points on a
transmission line. t
(flight)
= length × t
pd
t
pd
Propagation delay – delay per unit length of a signal traveling down a transmission
line, expressed by the formula t
pd
= Z
o
× C
o
Z
o
Characteristic impedance – impedance of a transmission line, as defined by
Z
o
+ L
o
ńC
o
Ǹ
Z
o(eff)
Effective impedance – impedance of a transmission line when external capacitance
is added at fixed intervals along the line.
Z
o(eff)
+ L
o
ń(C
o
) C
d
)
Ǹ