Output driver

Details Output driver Output driver

2000-08-28

2001-11-20

Cunningham, Terry D. (Department: 2816)

Miscellaneous active electrical nonlinear devices, circuits, and

Signal converting, shaping, or generating

Current driver

C327S376000, C327S377000, C327S384000, C326S086000, C326S087000, C326S027000, C326S030000

Reexamination Certificate

active

06320433

ABSTRACT:

TECHNICAL FIELD OF THE INVENTION
This invention relates generally to the field of integrated circuits and more particularly to output drivers.
BACKGROUND OF THE INVENTION
Integrated circuits often employ driver circuitry to drive output loads such as those connected to a bus or backplane. Applications having long transmission lines connected to the driver may cause undesirable reflections back to the driver circuitry, resulting in ringing on the outputs of an integrated circuit. Therefore, an output driver is needed that efficiently reduces ringing but maintains high speed operation.
SUMMARY OF THE INVENTION
One aspect of the invention is an integrated circuit comprising a digital circuit operable to generate first signal and a driver circuit coupled to the signal generating circuit and to an output load. The driver circuit comprises a first transistor operable to sink a first amount of current from an output node when activated and a second transistor operable to sink a second amount of current from the output node when activated. The driver circuit also comprises a third transistor coupled to the first transistor and operable to activate the first transistor and the second transistor in response to a transition of a first signal. The driver circuit further comprises at least one resistive element coupled to the second transistor and to the third transistor that is operable to delay activation of the second transistor until after activation of the first transistor.
The invention provides several important advantages. Various embodiments of the invention may have none, some, or all of these advantages. The invention may control ringing on outputs without interfering significantly with switching speeds of an integrated circuit. By gradually turning on a series of output driver transistors, ringing is reduced. The invention achieves these advantages with circuitry that does not consume significant area on an integrated circuit. The invention allows integrated circuits to be coupled to long transmission lines. Integrated circuits, including applications using DIMM technology, may also be designed without detailed knowledge of transmission line lengths.


REFERENCES:
patent: 5140194 (1992-08-01), Okitaka
patent: 5585740 (1996-12-01), Tipon
patent: 5726583 (1998-03-01), Kaplinsky
patent: 5838186 (1998-11-01), Inoue

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