A system includes: a power supply; an adaptively biased power event detection comparator; and an adaptive bias circuit for the adaptively biased power event detection comparator. The adaptively biased power event detection comparator is configured to compare a first input corresponding to a voltage level of the power supply with a second input corresponding to a reference voltage. The adaptive bias circuit is configured to increase a bias current for the adaptively biased power event detection comparator based on the voltage level of the power supply decreasing to be closer to the reference voltage.

A system includes a housing, a sensing electrode disposed within the housing, and a connecting electrode. The system also includes a capacitive sensing circuit galvanically connected to the connecting electrode at a first port, but not to the sensing electrode. The capacitive sensing circuit is configured to determine a first capacitance between the first port and a ground. The first capacitance includes a variable capacitance between the connecting electrode and a person when the person is touching the housing.

A method of capacitive sensing may include transmitting a first sensing signal along a first transmitter electrode among various transmitter electrodes of an input device. The method may further include obtaining, using various receiver electrodes in the input device, a first resulting signal in response to the first sensing signal being transmitted along the first transmitter electrode. The method may further include obtaining a second resulting signal from a second transmitter electrode among the transmitter electrodes. The method may further include determining, using the second resulting signal, interference along the second transmitter electrode. The method may further include adjusting, using the interference along the second transmitter electrode, the first resulting signal to produce an adjusted resulting signal. The method may further include determining, using the adjusted resulting signal, positional information regarding a location of an input object in a sensing region of the input device.

Electrodes Ex and regions of top plate opposed to electrodes Ex constitute switches SWx that have capacitances varying when the regions of top plate are depressed from top plate toward electrodes Ex. Depression detection circuit calculates the capacitance change amounts of switches SWx indicating changes of the capacitances from a reference value. Depression detection circuit calculates the maximum value and sum of the capacitance change amounts of switches SWx. When the capacitance change amount of at least one switch SWx exceeds threshold TH_EDGE and a situation in which the ratio of the maximum value to the sum is equal to or greater than threshold COMP_LEVELx has lasted for the number of repetitions in SW_DET_COUNT, depression detection circuit determines that the switch having the maximum value of the capacitance change amount is in a depressed state.

A transform is used to transform raw sensor data from the time domain to the frequency or sequency domain. The transformed data falls into several signal bins. The transformed data in at least one of the signal bins is analyzed to determine whether a touch event or release event has occurred.

A capacitive vehicle seat occupancy detection and classification system includes an impedance measurement circuit and a control and evaluation unit. The impedance measurement circuit is configured for providing periodic electrical measurement signals to a capacitive sensor of N different fundamental frequencies, wherein N is a natural number of at least 3, and to determine a complex impedance from each of determined sense currents in the capacitive sensor. The control and evaluation unit is configured to determine a seat occupancy class for each one of the complex impedances determined at the at least N different fundamental frequencies, and to determine a final seat occupancy class derived by a majority decision among the determined seat occupancy classes.

A capacitive sensor includes a sensor head, and a capacitance measurement unit. The sensor head includes a sheet-shaped base material, a measuring electrode on one surface of the base material, and a guard electrode on another surface of the base material. The guard electrode is positioned opposing to the measuring electrode in alignment with the same. The guard electrode has an outer periphery at least partially larger than an outer periphery of a shape formed by the measuring electrode. The capacitance measurement unit supplies an input voltage signal having a predetermined cycle to the measuring electrode, converts an output current signal output therefrom corresponding to the input voltage signal into an output voltage to output the output voltage as an output voltage signal, while supplying a voltage signal having a phase identical to a phase of the input voltage signal.

A system includes: a power supply; an adaptively biased power event detection comparator; and an adaptive bias circuit for the adaptively biased power event detection comparator. The adaptively biased power event detection comparator is configured to compare a first input corresponding to a voltage level of the power supply with a second input corresponding to a reference voltage. The adaptive bias circuit is configured to increase a bias current for the adaptively biased power event detection comparator based on the voltage level of the power supply decreasing to be closer to the reference voltage.

A capacitance detection device includes a first voltage output circuit configured to output a first alternating current voltage supplied to a shield electrode provided proximate to a detection electrode, a second voltage output circuit configured to output a second alternating current voltage whose frequency and phase are the same as that of the first alternating current voltage and whose amplitude is less than that of the first alternating current voltage, and a current output circuit configured to output a driving current Is to the detection electrode so that the difference between the voltage of the detection electrode and the second alternating current voltage becomes smaller, and output a detection signal corresponding to the driving current. The second voltage output circuit outputs a second alternating current voltage whose amplitude is adjusted so that the driving current in the absence of the object proximate to the detection electrode.

A touch sensitive capacitive keypad system (100) is provided with an analog-to-digital converter, a keypad sensing electrode (114) coupled to measure capacitance voltages using a configurable electrode scan rate, and a controller (120) configured to provide scan-rate independent capacitance voltage measurements from the keypad sensing electrode to the analog-to-digital converter when there is a change in the configurable electrode scan rate by repetitively sampling a capacitance voltage measurements (e.g., 524a-f) from the keypad sensing electrode over a plurality of sequential electrode scan cycles and then discarding a predetermined number of the capacitance voltage measurements (e.g., 524a-b) to generate the scan-rate independent capacitance voltage measurements (e.g., 524c-f) that are provided to the analog-to-digital converter.