Method and apparatus for protecting circuits subjected to high voltage
US5929667A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jun 10, 1997 |
| Grant date | Jul 27, 1999 |
| Priority date | — |
| Expiry date | Jun 10, 2017 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH03K19/00315
- WIPO fieldBasic communication processes
- WIPO sectorElectrical engineering
Abstract
A CMOS off-chip driver circuit and a method of operating the circuit are provided. The circuit has two pull-down transistors and two pull-up transistors, each pull-up transistor has a gate. A voltage source provides voltage at a logic-high output voltage of approximately 3.3 volts. An output terminal is provided. Initially, a logic-low output voltage is applied to the gate of each of the two pull-up transistors. A condition is detected in which the voltage of the output terminal is greater than a predetermined threshold voltage. The predetermined threshold voltage is between approximately 2.5 volts and approximately 3.3 volts. The voltage applied to the gate of each of the pull-up transistors is raised to an intermediate level that is greater than the logic-low output voltage and less than the logic-high output voltage while the condition is detected. The intermediate level may be approximately 1.5 volts. A clamping mechanism is provided for sinking current from the output terminal to the voltage source, when the voltage of the output terminal is greater than the logic-high output voltage. The clamping mechanism sources current to the output terminal from a ground conductor that pr…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.