CMOS output buffer with feedback control on sources of pre-driver stage
US6255867A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Feb 23, 2000 |
| Grant date | Jul 3, 2001 |
| Priority date | — |
| Expiry date | Feb 23, 2020 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH03K19/00361
- WIPO fieldBasic communication processes
- WIPO sectorElectrical engineering
Abstract
Ground and power-supply bounce are reduced for a CMOS output buffer. An n-channel driver transistor and a p-channel driver transistor are attached to the output pad. The gate of the n-channel driver transistor is driven by a pre-driver inverter. The pre-driver is a CMOS inverter except that the p-channel source is connected to power through a p-channel and an n-channel source-control transistor in parallel. The n-channel source-control transistor has its gate connected to power so that it remains on. The p-channel source-control transistor has its gate driven by feedback. The feedback is buffered from the output pad, or inverted from the gate of the driver transistor. When the output buffer switches, only the n-channel source-control transistor is initially on, so the current charging the driver gate is limited. The driver turns on slowly at first. Later, the feedback turns on the p-channel source-control transistor, increasing (doubling) the current to charge the driver gate. Thus the driver turns on more rapidly than at first, reducing di/dt and noise. Split driver transistors, and source control on the n-channel transistor are alternatives.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.