Utilizing the LC oscillator of a frequency synthesizer as an injection source for crystal oscillator startup
US11699974B1 · kind B1 · utility
Assignee
Inventors
Key dates
| Filing date | Jun 29, 2022 |
| Grant date | Jul 11, 2023 |
| Priority date | — |
| Expiry date | Jun 29, 2042 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH03B2201/025
- WIPO fieldBasic communication processes
- WIPO sectorElectrical engineering
Abstract
A frequency synthesizer on an integrated circuit provides a local oscillator (LO) signal for RF operations and also functions as an injection clock signal source during crystal oscillator startup. The integrated circuit goes into a sleep mode in which the crystal oscillator is off and responsive to a wakeup event the crystal oscillator starts up again using the injection clock signal sourced from the frequency synthesizer. Parameters that cause the injection clock signal to match the crystal oscillator frequency are stored. The frequency synthesizer includes a phase-locked loop having an LC oscillator. A digital to analog converter controls the LC oscillator during injection. During an initial power up of the integrated circuit, a PLL in the frequency synthesizer locks to the crystal oscillator frequency to determine the parameters to store for injection.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.