Differential charge pump for phase locked loop circuits
US5831484A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Mar 18, 1997 |
| Grant date | Nov 3, 1998 |
| Priority date | — |
| Expiry date | Mar 18, 2017 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH03L7/0896
- WIPO fieldBasic communication processes
- WIPO sectorElectrical engineering
Abstract
A differential charge pump is provided for use with phase locked loop (PLL) circuits including a differential loop filter and a common mode bias circuit for maintaining a predetermined bias voltage value on a high voltage filter side of the loop filter. The differential charge pump includes a reference current source. First and second current mirrors are coupled to the reference current source for providing a first mirror current and a second mirror current. A first switching transistor coupled to the first current mirror receives an input UP signal conducts current from a first side of the loop filter. A second switching transistor coupled to the second current mirror receives an input DOWN signal and conducts current from a second side of the loop filter. The first and second current mirror and switching transistors are formed by N-channel metal oxide semiconductor (NMOS) devices. The differential charge pump enables a large differential output voltage with low phase error.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.