Electronic digital logic circuitry – Interface – Current driving
Reexamination Certificate
2000-02-18
2001-10-16
Tokar, Michael (Department: 2819)
Electronic digital logic circuitry
Interface
Current driving
C326S086000, C326S030000, C370S282000, C370S284000, C375S219000
Reexamination Certificate
active
06304106
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a Complementary Metal Oxide Semiconductor (CMOS) bi-directional current mode differential link with precompensation.
DESCRIPTION OF THE RELATED ART
U.S. Pat. No. 5,666,354 issued Sep. 9, 1997 and assigned to the present assignee, discloses a full-duplex, differential, bi-directional communications link for simultaneously transmitting differential data between electronic devices. Each transceiver coupled to the communications channel comprises a Complementary Metal Oxide Semiconductor (CMOS) differential driver and receiver. The differential driver provides constant CMOS voltage sources for providing stable data signal transmission at reduced voltage levels. Voltage sources providing a data signal voltage different from the desired data signal voltage can be placed into a high impedance mode to allow the desired data signal voltage to be transmitted on the common line. The differential receiver includes self-biasing feedback circuitry to provide biasing voltages to the circuit while avoiding manufacturing difficulties associated with providing precise bias voltages. The complementary amplifier structure of the receiver provides an increased common mode noise tolerance. The receiver further includes signal separation circuitry to separate the desired recipient signals on the communications channel from those signals which are driven to another differential receiver on the far end.
While the above-identified U.S. patent overcomes many disadvantages of conventional arrangements, a need exists for a Complementary Metal Oxide Semiconductor (CMOS) bi-directional current mode differential link with precompensation.
SUMMARY OF THE INVENTION
A principal object of the present invention is to provide a Complementary Metal Oxide Semiconductor (CMOS) bi-directional current mode differential link with precompensation. Other important objects of the present invention are to provide such a Complementary Metal Oxide Semiconductor (CMOS) bi-directional current mode differential link with precompensation substantially without negative effect; and that overcomes many of the disadvantages of prior art arrangements.
In brief, a Complementary Metal Oxide Semiconductor (CMOS) current mode differential link with precompensation is provided. The Complementary Metal Oxide Semiconductor (CMOS) bi-directional current mode differential link with precompensation includes a CMOS driver receiving a data input and having an output coupled to a transmission line. A CMOS replica driver receives the data input and provides a replica driver output substantially equal to the CMOS driver output. A CMOS receiver is coupled to both the transmission line and replica driver output. The CMOS receiver subtracts the replica driver output from a signal at the transmission line. The CMOS driver and the CMOS replica driver include a plurality of parallel current sources. Each of the current sources is arranged to send positive or negative current through a load responsive to an applied control signal.
In accordance with features of the invention, the use of the plurality of parallel current sources allows the CMOS driver to effectively implement precompensation. The output current of the CMOS driver is a function of a data bit and at least one previous data bit.
REFERENCES:
patent: 5666354 (1997-09-01), Cecchi et al.
patent: 5778204 (1998-07-01), Van Brunt et al.
patent: 5900752 (1999-05-01), Mar
patent: 6184714 (2001-02-01), Kirsch et al.
Cecchi Delbert Raymond
Hanson Charles C.
Preuss Curtis Walter
International Business Machines - Corporation
Pennington Joan
Tan Vibol
Tokar Michael
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