Capacitance to frequency converter
First Claim
1. A capacitance to frequency converter, comprising:
- a switching capacitor circuit to charge a sensing capacitor and to transfer charge from the sensing capacitor to a charge dissipation circuit via a circuit node;
a comparator coupled to the charge dissipation circuit to compare a potential at the circuit node to a reference voltage; and
a signal generator coupled to an output of the comparator and to the charge dissipation circuit, the signal generator responsive to the output of the comparator to generate a signal fed back to control the charge dissipation circuit, wherein a frequency of the signal is proportional to a capacitance of the sensing capacitor, and wherein the charge dissipation circuit comprises a modulation capacitor coupled to the circuit node and a current source coupled to selectively discharge the modulation capacitor in response to the signal.
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Accused Products
Abstract
A capacitance to frequency converter includes a switching capacitor circuit, a charge dissipation circuit, a comparator, and a signal generator. The switching capacitor circuit charges a sensing capacitor and transfers charge from the sensing capacitor to a circuit node of the charge dissipation circuit. The comparator is coupled to the charge dissipation circuit to compare a potential at the circuit node to a reference voltage. The signal generator is coupled to an output of the comparator and to the charge dissipation circuit. The signal generator is responsive to the output of the comparator to generate a signal fed back to control the charge dissipation circuit. A frequency of the signal is proportional to a capacitance of the sensing capacitor.
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Citations
22 Claims
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1. A capacitance to frequency converter, comprising:
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a switching capacitor circuit to charge a sensing capacitor and to transfer charge from the sensing capacitor to a charge dissipation circuit via a circuit node; a comparator coupled to the charge dissipation circuit to compare a potential at the circuit node to a reference voltage; and a signal generator coupled to an output of the comparator and to the charge dissipation circuit, the signal generator responsive to the output of the comparator to generate a signal fed back to control the charge dissipation circuit, wherein a frequency of the signal is proportional to a capacitance of the sensing capacitor, and wherein the charge dissipation circuit comprises a modulation capacitor coupled to the circuit node and a current source coupled to selectively discharge the modulation capacitor in response to the signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A method of converting a capacitance value to a frequency value, the method comprising:
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reciprocally switching charge into a first capacitor having the capacitance value and out of the first capacitor into a second capacitor; selectively modulating a frequency of a pulse signal in response to the charge accumulated on the second capacitor; and selectively discharging the charge from the second capacitor in response to the pulse signal. - View Dependent Claims (12, 13, 14, 15, 16)
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17. An apparatus, comprising:
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a switching capacitor circuit to charge a first capacitor and to transfer charge between the first capacitor and a modulation capacitor; a comparator coupled to the modulation capacitor to compare a potential on the modulation capacitor to a first voltage and to generate a modulation signal; a pulse generator coupled to the comparator to receive the modulation signal and to generate a feedback signal responsive to the modulation signal; and a discharging circuit coupled to selectively discharge the modulation capacitor responsive to the feedback signal. - View Dependent Claims (18, 19, 20, 21, 22)
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Specification