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US 8,283,934 B2Granted
Capacitance sensor for detecting a charge voltage of a multi-capacitor circuit
AssigneeFujitsu Semiconductor Limited
InventorKazunori Nishizono
Life of this patent
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Abstract
A capacitance sensor includes a first charging voltage detector configured to detect a change in a voltage loaded into a first capacitor between an electrode and a ground terminal a second charging voltage detector configured to detect a change in a voltage loaded into a second capacitor among a plurality of electrodes and a determiner configured to generate a determination signal based on a detection voltage transmitted from each of the first charging voltage detector and second charging voltage detector.
Claims16
A capacitance sensor comprising:
- a first charging voltage detector configured to detect a change in a voltage loaded into a first capacitor between a first electrode and a ground terminal;
- a second charging voltage detector configured to detect a change in a voltage loaded into a second capacitor between the first electrode and a second electrode;
- and
- a determiner configured to generate a determination signal based on a detection voltage transmitted from each of the first charging voltage detector and second charging voltage detector,
- wherein the first charging voltage detector includes:
- a first comparator configured to compare a first detection voltage obtained from the first detection operation of the detection circuit with a first threshold;
- a first counter configured to count an output from the first comparator,
- the second charging voltage detector includes:
- a second comparator configured to compare a second detection voltage obtained from the second detection operation of the detection circuit with a second threshold;
- a second counter configured to count an output from the second comparator,
- wherein the determiner is configured to output the determination signal when detecting an output of the first counter and an output of the second counter.
8 more elements
A capacitance sensor comprising:
- a first charging voltage detector configured to detect a change in a voltage loaded into a first capacitor between a first electrode and a ground terminal;
- a second charging voltage detector configured to detect a change in a voltage loaded into a second capacitor between the first electrode and a second electrode;
- and
- a determiner configured to generate a determination signal based on a detection voltage transmitted from each of the first charging voltage detector and second charging voltage detector,
- wherein the first charging voltage detector includes a detection circuit configured to detect the voltage loaded into the first capacitor, and the second charging voltage detector includes a detection circuit configured to detect the charge in voltage loaded into the second capacitor,
- wherein a first detection operation configured to detect the charge in voltage loaded into the first capacitor, and a second detection operation configured to detect the charge in voltage loaded into the second capacitor, are carried out in a time division manner by a shared detection circuit,
- wherein the shared detection circuit includes:
- an operational amplifier having an output terminal and an input terminal coupled one of the first capacitor and second capacitor selectively;
- and
- a first switch coupled between the input terminal and the output terminal,
- wherein, when the first switch becomes conductive, a low potential side reference voltage is supplied to the first and second capacitors and, when the first switch becomes non-conductive, a high potential side reference voltage is supplied to the first and second capacitors.
8 more elements
Dependencies are inferred from the claim text.