Digitally-controlled crystal oscillator circuit
US7868710B1 · kind B1 · utility
Assignee
Inventors
Key dates
| Filing date | Feb 4, 2009 |
| Grant date | Jan 11, 2011 |
| Priority date | — |
| Expiry date | Apr 30, 2029 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH03B5/366
- WIPO fieldBasic communication processes
- WIPO sectorElectrical engineering
Abstract
The present invention relates to a digitally-controlled crystal oscillator (DCXO) circuit having control circuitry, an active core, and a pair of thermometer-coded switched-capacitor circuits (TCSCCs), each of which is coupled to the active core and to a crystal. The active core, the crystal, and the pair of TCSCCs form a DCXO, which provides an output signal having an output frequency. Each TCSCC includes multiple capacitive elements, which are selected by a respective control signal from the control circuitry to control the output frequency. The DCXO circuit may be integrated into a digital integrated circuit (IC) without need for a digital-to-analog converter (DAC), and may be used with a wide range of crystal types. By using thermometer-coding, the pair of TCSCCs provides monotonic frequency tuning behavior. Further, by utilizing different types of tuning steps, the DCXO may have a wide tuning range with high resolution.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.