Programmable Crystal Oscillator
First Claim
Patent Images
1. An oscillator circuit comprising:
- a first terminal;
a second terminalan inverter, a resistor and a crystal coupled in parallel between the first and second terminals;
a first load capacitor coupled between the first terminal and a first voltage supply terminal;
a second load capacitor coupled between the second terminal and the first voltage supply terminal;
a trim circuit that includes a first switch coupled to the first terminal, a second switch coupled to the second terminal, and a first trim capacitor coupled between the first and second switches.
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Abstract
A crystal oscillator circuit having a parallel resonant frequency that is adjustable by switching trim capacitors in parallel with a crystal.
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Citations
14 Claims
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1. An oscillator circuit comprising:
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a first terminal; a second terminal an inverter, a resistor and a crystal coupled in parallel between the first and second terminals; a first load capacitor coupled between the first terminal and a first voltage supply terminal; a second load capacitor coupled between the second terminal and the first voltage supply terminal; a trim circuit that includes a first switch coupled to the first terminal, a second switch coupled to the second terminal, and a first trim capacitor coupled between the first and second switches. - View Dependent Claims (2, 3, 4, 5, 6, 11)
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7. An oscillator circuit comprising:
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a first terminal; a second terminal an inverter, a resistor and a crystal coupled in parallel between the first and second terminals; a first load capacitor coupled between the first terminal and a first voltage supply terminal; a second load capacitor coupled between the second terminal and the first voltage supply terminal; and a trim circuit comprising a plurality of trim capacitors and means for selectively coupling the trim capacitors between the first terminal and the second terminal. - View Dependent Claims (8, 9, 10)
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12. A method of adjusting the parallel resonant frequency of an oscillator circuit having a crystal, the method comprising:
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closing a first switch to couple a first terminal of a first trim capacitor to a first terminal of the crystal; and closing a second switch to couple a second terminal of the first trim capacitor to a second terminal of the crystal, whereby closing the first and second switches couples the first trim capacitor in parallel with the crystal. - View Dependent Claims (13, 14)
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Specification