Electronic digital logic circuitry – Signal sensitivity or transmission integrity – Output switching noise reduction
Reexamination Certificate
1999-09-23
2001-06-26
Wamsley, Patrick (Department: 2819)
Electronic digital logic circuitry
Signal sensitivity or transmission integrity
Output switching noise reduction
C326S026000, C326S028000, C326S031000, C326S086000, C326S087000, C327S310000, C327S312000
Reexamination Certificate
active
06252418
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field
The present invention relates to electronic circuits, and in particular, to electronic noise suppression circuits.
2. Description of Related Art
As engineers seek ever increasing speeds in VLSI chips, complex problems continue to rise to the forefront. For example, as process feature sizes continue to shrink, metallurgical limitations are continually raising line-to-line interconnect coupling effects, leading to increased concern over signal noise and noise tolerances. Design engineers continually fight and solve problems relating to signal noise.
Signal noise can take several forms. Due to coupling effects, signals can bounce in one or more of four distinct directions: above ground, below the supply, below ground, and above the supply. Above-ground signal noise and below-supply signal noise can cause false switching events if the coupling effects cause a signal to cross the switching threshold of a given destination circuit. Below-ground signal noise and above-supply signal noise can cause loss of state in some types of latch circuits.
Therefore, it would be advantageous to provide an active circuit that can reduce noise effects, such as those produced by line-to-line interconnect coupling, and it would be particularly advantageous to provide an active circuit to reduce above-supply signal noise and below-ground signal noise.
SUMMARY OF THE INVENTION
A noise suppression circuit for suppressing noises above and below reference voltages is provided. The noise suppression circuit for suppressing noises includes a clamping transistor, a feedback circuit, and a presetting means for presetting an internal latch of the noise suppression circuit to a predetermined state. The predetermined state is a high state or a low state depending upon the type of noise suppression accomplished by the circuit. After the occurrence of a noise coupling event, the clamping transistor restores the state of a data input of a circuit to which the suppression circuit is providing protection. The feedback circuit then turns off the clamping transistor after a predetermined amount of time.
REFERENCES:
patent: 5065048 (1991-11-01), Asai et al.
patent: 5646557 (1997-07-01), Runyon et al.
patent: 5734277 (1998-03-01), Hu et al.
patent: 5793226 (1998-08-01), Park et al.
patent: 5933021 (1999-08-01), Mohd
Durham Christopher McCall
Klim Peter Juergen
Schmidt Shon Alan
Carwell Robert M.
International Business Machines - Corporation
Tan Vibol
Wamsley Patrick
Yee Duke W.
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