Circuit for minimizing turn-on time of temperature compensated crystal oscillator
US5977840A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Apr 29, 1998 |
| Grant date | Nov 2, 1999 |
| Priority date | — |
| Expiry date | Apr 29, 2018 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH03L3/00
- WIPO fieldBasic communication processes
- WIPO sectorElectrical engineering
Abstract
A temperature compensated crystal oscillator with an improved phase noise characteristic and a fast start up time includes a large time constant low-pass filter coupled to a temperature compensation circuit. At start up the low pass filter is effectively bypassed to enable the temperature compensation voltage and oscillator output frequency to settle quickly. A capacitance in the low-pass filter is precharged by a precharge circuit to match the temperature compensation voltage without disturbing the temperature compensation circuit and the concurrent settling of the oscillator. When the capacitance is fully charged, the low-pass filter is enabled without unsettling the oscillator output frequency.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.