State-dependent discharge path circuit
US5184034A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Dec 6, 1991 |
| Grant date | Feb 2, 1993 |
| Priority date | — |
| Expiry date | Dec 6, 2011 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH03K19/09448
- WIPO fieldBasic communication processes
- WIPO sectorElectrical engineering
Abstract
A circuit for use in connection with tristate output buffers in order to provide concurrently for fast discharge of the output pulldown transistor base and at the same time for building in protection against reverse breakdown in the pulldown transistor. The innovation consists of providing a two discharge paths to ground for the base of the output pullup transistor. A low-capacitance path is activated only while the output buffer is in its active mode. In the preferred embodiment of the invention, this low discharge path consists of two CMOS transistors in series, one of which is controlled by the enable signal input E of the buffer circuit and the other by the data signal input V.sub.IN of the buffer circuit. The other path to ground is available whenever the data signal input V.sub.IN is low, regardless of whether the buffer is in its active or inactive mode. This other path provides discharge protection for the base of the pullup transistor for the buffer in its inactive mode, and has incorporated into it reverse breakdown protection in the form of voltage drop devices such as forward-biased diodes.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.