Bus-isolating pre-charge buffer

Abstract

A bus line is divided into at least first and second bus segments that are coupled together via a precharge buffer, each segment seeing less effective RC than if segmentation were not present. The precharge buffer provides first and second output buffer lines (or segments) that are monitored and cross-coupled through the buffer such that each line is pulled-up or pulled-down substantially simultaneously to keep equivalent states in each. Feedback provided by the cross-coupling further hastens the process of bus pull down. Still further acceleration of the pulldown process can result by sensing bus pulldown at trip point that is higher than a conventional logic level trip point. Segmenting the bus and coupling the segments with a precharge buffer results in less equivalent RC being presented to each bus segment. Thus, effective shunt capacitance is reduced, allowing use of downsized transistors coupled to the output buffer lines to pull down the bus segments. This saves integrated circuit chip area, reduces pulldown surge current and ground bounce. Further, the decreased load capacitance achieved by using smaller pulldown load devices reduces capacitive bus loading, and thus contributes to a more rapid change of bus state. Alternatively, for a given pulldown current, the present invention permits a segmented bus to be pulled down more rapidly than a conventional non-segmented bus configuration.

Dependencies are inferred from the claim text.