Charge-pump phase-locked loop with DC current source
US6040742A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Sep 1, 1998 |
| Grant date | Mar 21, 2000 |
| Priority date | — |
| Expiry date | Sep 1, 2018 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04L7/033
- WIPO fieldBasic communication processes
- WIPO sectorElectrical engineering
Abstract
A phase-locked loop (PLL) has a phase detector (PD), a charge pump, a loop filter, and a voltage-controlled oscillator (VCO). The PD generates DOWN pulses based on differences in phase between an input signal and a feedback signal. The charge pump has an UP current source that generates a DC UP current and a DOWN current source that generates a DOWN current based on the DOWN pulses received from the phase detector. The charge pump generates a charge-pump current based on the DC UP current and the DOWN current. The loop filter receives the charge-pump current and generates a loop-filter voltage based on a net accumulation of charge from the charge-pump current. The VCO receives the loop-filter voltage and generates an output signal whose frequency is based on the loop-filter voltage, wherein the feedback signal is generated from the output signal. By using a DC UP current source, the PLLs of the present invention are able to operate at higher frequencies than conventional charge-pump PLLs, since the UP current source in the charge pump of a conventional PLL responds less quickly to PD pulses than does a conventional DOWN current source, due to mobility differences between holes and …
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.