Electronic digital logic circuitry – Interface – Current driving
Reexamination Certificate
1999-05-28
2001-01-23
Mai, Son (Department: 2818)
Electronic digital logic circuitry
Interface
Current driving
C326S087000, C327S108000, C327S109000
Reexamination Certificate
active
06177809
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field Of The Invention
The present invention relates to semiconductor integrated circuits, and more particularly to input/output driver circuits for integrated circuits.
2. Background Art
U.S. Pat. No. 4,855,623 issued Aug. 8, 1989 to Flaherty entitled OUTPUT BUFFER HAVING PROGRAMMABLE DRIVE CIRCUIT discloses an output buffer circuit for providing selected output driving characteristics. A plurality of input terminals receive control and data signals and are connected to an output terminal through a plurality of interconnected driver transistors. Drive selector circuitry is responsive to control signals to selectively vary the connections of the driver transistors to the output terminal.
U.S. Pat. No. 5,153,450 issued Oct. 6, 1992 to Ruetz entitled PROGRAMMABLE OUTPUT DRIVE CIRCUIT discloses a programmable output driver circuit having multiple drive capabilities for optimizing noise margins at different frequencies. The circuit includes a plurality of signal paths in parallel, each comprising a driver unit having a pull-down and pull-up transistor. During operation, selected signal paths are disabled to reduce noise at lower frequencies.
U.S. Pat. No. 5,486,782 issued Jan. 23, 1996 to Chan entitled TRANSMISSION LINE OUTPUT DRIVER discloses a push-pull output driver circuit that includes a pair of low current output circuits connected in parallel with a pair of high current series connected devices. In response to a pulse transition at the driver circuit input, one of the high current devices is turned on to change the state of the output signal. When the output signal has reached a steady state, a low current device is turned on and the high current device is turned off such that the low current maintains the output signal state.
U.S. Pat. No. 5,498,977 issued Mar. 12, 1996 to Pickup entitled OUTPUT DRIVER HAVING PROCESS, VOLTAGE AND TEMPERATURE COMPENSATION FOR DELAY AND RISETIME discloses a chip wherein the effects of Process, supply Voltage and Temperature (PVT) variables are minimized by a table of predrive gain used to compensate for the effect of the PVT variables.
SUMMARY OF THE INVENTION
An object of the present invention is to provide improved input/output (I/O) circuitry that provides appropriate driver strength for an off-chip driver (OCD) circuit.
Another object of the present invention is to provide an improved I/O circuit that provides driver strength as a function of driving load or changing operating conditions such as power supply, or circuit degradation.
Still another object of the present invention is to provide an improved I/O circuit that continuously monitors OCD circuit operating conditions over time and optimizes the power/performance circuit factor.
Other objects, features, advantages and benefits of the present invention will become apparent in the following description taken in conjunction with the following drawings. It is to be understood that the foregoing general description and the following detailed description are exemplary and explanatory but are not to be restrictive of the invention.
REFERENCES:
patent: 4855623 (1989-08-01), Flaherty
patent: 5153450 (1992-10-01), Ruetz
patent: 5486782 (1996-01-01), Chan
patent: 5498977 (1996-03-01), Pickup
patent: 5917340 (1999-06-01), Manohar et al.
patent: 5994922 (1999-11-01), Aoki et al.
Bertin Claude L.
Bonaccio Anthony R.
Fifield John A.
Kalter Howard L.
Mandelman Jack A.
Goodwin John J.
International Business Machines - Corporation
Mai Son
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