Latched active fail-safe circuit for protecting a differential receiver
US6650149B1 · kind B1 · utility
Assignee
Inventor
Key dates
| Filing date | Aug 15, 2002 |
| Grant date | Nov 18, 2003 |
| Priority date | — |
| Expiry date | Aug 15, 2022 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH03K19/007
- WIPO fieldBasic communication processes
- WIPO sectorElectrical engineering
Abstract
A fail-safe circuit for a differential receiver can tolerate noise. A latch is enabled when both differential inputs V+, V− rise above a reference voltage that is close to Vcc. The latch, once enabled, is set by an offset amplifier, signaling the fail-safe condition. The offset amplifier sets the latch when V+ is above or equal to V−. The differential amplifier has a small offset voltage to allow the latch to remain set when V+ and V− are equal in voltage. An output from a differential amplifier receiving V+ and V− can be blocked by a gate when the fail-safe condition is latched. Pullup resistors pull V+, V− to Vcc when an open failure occurs. The latch remains set when common-mode noise occurs on V+, V−, preventing noise from prematurely disabling the fail-safe condition. Such noise coupled into a broken cable is usually common-mode.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.