Voltage-controlled crystal oscillator (VCXO) using MOS varactors coupled to an adjustable frequency-tuning voltage
US6628175B1 · kind B1 · utility
Assignee
Inventors
Key dates
| Filing date | Mar 27, 2002 |
| Grant date | Sep 30, 2003 |
| Priority date | — |
| Expiry date | Mar 27, 2022 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH03K3/354
- WIPO fieldBasic communication processes
- WIPO sectorElectrical engineering
Abstract
A voltage-controlled crystal oscillator (VCXO) has variable load capacitors on the crystal nodes. The variable load capacitors are p-channel or n-channel transistors with their source and drain nodes connected to a crystal node. The gates are driven by an input voltage that is generated from a full-swing control voltage by a voltage conversion circuit. The input voltage has a half-swing of only half of the power-supply voltage, or VDD/2. The input voltage driving n-channel capacitors swings from VDD to VDD/2, which is just above the source voltage of VDD/2 on the crystal node and ensures that the n-channel capacitors remain on for most of the range. A series of resistors can divide the input voltage into a series of differing voltages that drive gates of multiple n-channel capacitors that have their source/drains connected in parallel to the crystal node. Capacitance increases as an n-channel capacitor channel turns on.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.