Invalidity dossier
US 5359235
Bus termination resistance linearity circuit
Current assignee: Hewlett Packard Development Co LP
Added 9/21/2026, 9:24:12 AM
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Patent summary
Title, assignee, inventors, filing/issue dates, abstract, and a plain-language overview of the claims.
Patent Overview — US 5,359,235 A
Title: Bus termination resistance linearity circuit
Patent number: US 5,359,235 A (application US 08/079,516)
Inventors: Joseph P. Coyle; William B. Gist
Original assignee: Digital Equipment Corporation
Dates: Priority/filing date 1993-06-18; granted/publication date 1994-10-25; anticipated expiration 2013-06-18. Legal status listed as "Expired – Lifetime" (a listing assumption, not a legal conclusion). Later reassignments listed are to Compaq Information Technologies Group, L.P., then Hewlett-Packard Development Company, L.P.; current assignee listed as Hewlett Packard Development Co LP.
Purpose and plain-language scope (from the supplied text): The invention relates generally to computer systems and more particularly to devices used to drive signals onto and receive signals from a computer bus. The excerpt frames the problem in bus performance terms: cycle time, settling time, reflections, and variation in semiconductor process characteristics (resistances, capacitances, currents, voltages, propagation delays) across lots and over time. Terminating a bus, it notes, requires a high-precision component but does not easily account for impedance variation due to processing or time, and end-termination still leaves portions of the bus between common conductors and individual devices unterminated, a source of reflections at higher speeds. The excerpt states that termination should have a linear relationship between the current provided and the voltage of the signal being terminated. It describes a programmable termination comprising means, responsive to a voltage reference signal representative of a desired impedance value, for providing control signals representative of the impedance, and means, responsive to those control signals, for providing the impedance — the latter having a non-linear relationship (sentence truncated). Technical classifications include H04L25/026 and G06F13/4086 (bus impedance matching, e.g. termination).
Not established by this excerpt: the complete claims, full written description, drawing content, specific circuit elements or embodiments, any prior-art references, prosecution history, enforceability, or the outcome of the listed reassignments. The text is explicitly marked as an excerpt with omitted material.
Generated 10/1/2026, 10:02:32 PM
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Assignment history
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Prior art
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Obviousness
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Extensions
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Derivative works
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