Output buffer with time varying source impedance for driving capacitively-terminated transmission lines
US6980021B1 · kind B1 · utility
Assignee
Inventors
Key dates
| Filing date | Jun 18, 2004 |
| Grant date | Dec 27, 2005 |
| Priority date | — |
| Expiry date | Jul 15, 2024 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04L25/026
- WIPO fieldDigital communication
- WIPO sectorElectrical engineering
Abstract
An output buffer for driving a capacitively-terminated transmission line produces a waveform which comprises a first portion during which the waveform transitions from a voltage V1 to a voltage V2; a second portion during which it remains fixed at V2; a third portion during which it transitions to a voltage V3; and a fourth portion during which it remains fixed at V3. The waveform is created within a unit interval whenever successive data bits transition between logic states. The first and second portions are generated with circuitry arranged such that V2 is maximized by reducing the buffer's output impedance. The fourth portion is generated with circuitry which has a non-zero output impedance preferably equal to the transmission line's characteristic impedance, to absorb transitions reflected back to the source circuitry by the capacitive termination.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.