Electronic digital logic circuitry – Signal sensitivity or transmission integrity – Bus or line termination
Reexamination Certificate
2002-03-12
2003-10-28
Tokar, Michael (Department: 2819)
Electronic digital logic circuitry
Signal sensitivity or transmission integrity
Bus or line termination
C326S086000, C326S090000, C370S282000, C370S284000, C375S219000
Reexamination Certificate
active
06639423
ABSTRACT:
FIELD
The present invention relates generally to integrated circuit interfaces, and more specifically to integrated circuit interfaces having current mode drivers.
BACKGROUND
Integrated circuits typically have dedicated interface circuits to communicate with other integrated circuits and other systems. These dedicated interface circuits are typically interconnected with conductors, commonly referred to as “signal lines” or “traces,” that carry signals from one integrated circuit to another. Some signal lines are “terminated” with a termination impedance that approximates the characteristic impedance of the signal line. These terminations can increase communication reliability by reducing unwanted signal reflections on the signal line. When the characteristic impedance of a signal line is uniform across its length, and the termination impedance “matches” the characteristic impedance of the signal line, signal reflections can be substantially reduced.
Signals that travel from one integrated circuit to another are becoming faster and faster. As signal speeds increase, the effects (unwanted reflections) of poorly terminated signal lines become more pronounced, and proper terminations become more important. In prior systems, signal lines are commonly terminated using external resistors coupled to the signal line outside the integrated circuit. These external resistors can.reduce reflections if chosen carefully, but can also take up a significant amount of space outside the integrated circuits. In systems that include many signal lines in need of termination, external resistors can consume a prohibitively large amount of space.
In addition to consuming space, external resistors typically require a system designer to compromise the quality of the termination. Signal line impedances vary from system to system, and external resistors typically exist at standard impedance values, thereby forcing the system designer to include external resistors that provide a compromised signal line termination.
For the reasons stated above, and for other reasons stated below which will become apparent to those skilled in the art upon reading and understanding the present specification, there is a need in the art for alternate integrated circuit interfaces and terminations.
REFERENCES:
patent: 6208161 (2001-03-01), Suda
patent: 6304106 (2001-10-01), Cecchi et al.
patent: 6344756 (2002-02-01), Cecchi et al.
Casper Bryan K.
Martin Aaron K.
Mooney Stephen R.
Intel Corporation
Schwegman Lundberg Woessner & Kluth P.A.
Tan Vibol
Tokar Michael
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