Digitally tunable capacitor
AssigneeMarvell International Ltd.
InventorJody Greenberg
Life of this patent
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Abstract
The disclosed device can contain a pair of switchable capacitors, one of which has the larger capacitance of the pair. Each of the switchable capacitors can include a capacitor in series with a switch. Both switchable capacitors can be connected in a parallel circuit that has a tunable capacitance. The ratio of the capacitances of the pair can approximately equal a ratio of mutually prime integers. In a particular case, the ratio of capacitances can approximately equal a ratio of two consecutive integers. The capacitance ratio can be called a weight or weight ratio. A switch controller can drive the pair of switchable capacitors with a pair of (M+1)-ary pulse width modulated signals, each of which has the same modulation period.
Claims20
A device, comprising:
- a first capacitor having a first capacitance;
- a second capacitor having a second capacitance, the second capacitor being connected in a parallel circuit with the first capacitor, the parallel circuit having a tunable capacitance;
- and
- a switch controller that is coupled to the first and second capacitors, the switch controller being configured to switch the first and second capacitors to adjust the tunable capacitance;
- and
- an offset capacitor having an offset capacitance, the offset capacitor being coupled to the switch controller and in parallel with the first and second capacitors, wherein the switch controller generates an offset pulse width modulation signal to turn on the offset capacitor for a full modulation period.
A method, comprising:
- controlling switching of a parallel circuit comprising first and second switchable capacitors by a switch controller to adjust a tunable capacitance of the parallel circuit, the first switchable capacitor having a first capacitance, the second switchable capacitor having a second capacitance and being connected in the parallel circuit with the first switchable capacitor and the switch controller;
- and
- generating an offset pulse width modulation signal by the switch controller to turn on an offset switchable capacitor for a full modulation period, the offset switchable capacitor being coupled in parallel with the first and second switchable capacitors.
Dependencies are inferred from the claim text.