Semiconductor Components Industries, LLC

Sanyo Electric Co., Ltd.

Sanyo Semiconductor Co., Ltd.

Kazuyuki Kobayashi

Yasuhiro Kaneta

Tatsuya Suzuki

Kumiko Fukai

Akinobu Onishi

Yasuhiro Hinokuma

Kengo Murase

There is offered a signal processing circuit for an electrostatic capacity type touch sensor which can improve the noise tolerance and adjust an offset in the output voltage. The signal processing circuit for the touch sensor is structured to include an alternating current power supply providing an excitation pad with an alternating voltage, an electric charge amplifier generating an output voltage Vout corresponding to a difference between a capacitance of a first capacitor formed between a first touch pad and the excitation pad and a capacitance of a second capacitor formed between a second touch pad and the excitation pad, and an offset adjustment circuit to adjust an offset in the output voltage Vout of the electric charge amplifier.

Signal processing circuit for electrostatic capacity type touch sensor

This invention offers a signal processing circuit of an electrostatic capacity type touch panel which is capable of switching between a differential input mode and a single input mode and has an extended adjustable range of an offset in the single input mode. The signal processing circuit of this invention includes a first sensor circuit of a differential input type, a second sensor circuit of a single input type, a third and fourth electrostatic capacitors that are variable capacitors for calibration to adjust the offset in an output voltage of the first sensor circuit, and a switching control circuit to control so as to put in operation one of the first and second sensor circuits. The switching control circuit also controls so that the third and fourth electrostatic capacitors for calibration are connected in parallel to each other when the second sensor circuit is put in operation.

Method of reducing offset in a capacitive touch panel capable of switching between a differential-input sensor circuit and single-ended sensor circuit

There is offered a signal processing circuit of the electrostatic capacity type touch panel which can eliminate duplication of components to reduce a cost of the components. A touch panelis formed on a glass substrate. Sensor circuitsA andB are arrayed in a Y direction, and sensor circuitsC andD are arrayed in an X direction on the periphery of the touch pane. Serial clock terminals SCL of the sensor circuitsA-D are connected to a serial clock lineall together, while serial data terminals SDA are connected to a serial data lineall together. A microcomputeris disposed on a PCB substrate outside the glass substrate. Data communication can be performed between the microcomputerand the sensor circuitsA-D through the serial clock lineand the serial data line

Capcitive touch panel with simultaneously enabled X- and Y-direction sensor circuits wherein in each sensor circuit the drive line is interdigitated with a plurality of sense lines

There is offered a signal processing circuit for an electrostatic capacity type touch sensor capable of detecting a larger number of locations with a smaller number of touch pads as well as improving noise immunity. A selection circuit selects either a signal from a combination of the first and second kinds of touch pads outputted through the first and second output terminals COand COin a touch panel or a signal from a combination of the third and fourth kinds of touch pads outputted through the third and fourth output terminals COand CO. An electric charge amplifier outputs first and second output voltages Vand Vcorresponding to a difference between capacitances of the touch pads on the touch panel based on the signals from the selected combination. A delta sigma type A/D converter converts the first and second output voltages Vand Vinto digital signals.

A semiconductor integrated circuit that is efficiently reduced in a noise level is offered. P-channel type MOS transistors Mand Mserving as differential input transistors have a thin gate oxide film in order to reduce the noise level. A protection circuit to protect the P-channel type MOS transistors Mand Mfrom overvoltage is formed including P-channel type MOS transistors Mand M. The P-channel type MOS transistor Mis a first protection transistor to protect the P-channel type MOS transistor Mfrom overvoltage, and is connected to a drain of the P-channel type MOS transistor M. The P-channel type MOS transistor Mis a second protection transistor to protect the P-channel type MOS transistor Mfrom overvoltage, and is connected to a drain of the P-channel type MOS transistor M

Semiconductor integrated circuit

The invention realizes certainly detecting two or more positions on a touch panel that are touched at the same time. A drive circuit selects one from X lines, and supplies an alternating drive voltage to the selected line. A multiplexer selects a first sense line and a second sense line from Y lines that extend to cross the X lines. A charge amplifier outputs an output voltage corresponding to a difference between a first capacitance between the first sense line and the X line selected by the drive circuit and a second capacitance between the second sense line and the X line selected by the drive circuit. A touch position is then detected based on the output voltage of the charge amplifier.

Signal processing circuit for electrostatic capacitor type touch sensor

There is offered a signal processing device of touch panel using an electrostatic capacity, which realizes improvement in noise tolerance and linear detection. An excitation pad, a first touch pad and a second touch pad are disposed on a substrate in a way that the excitation pad is interposed between the first and second touch pads. On the other hand, an alternating current power supply that provides the excitation pad with an alternating voltage through a wiring is provided on a sensor IC side of the signal processing device of touch panel. Also, there is provided an electric charge amplifier. The first touch pad is connected to a non-inverting input terminal (+) of the electric charge amplifier through an wiring, while the second touch pad is connected to an inverting input terminal (&#x2212;) of the electric charge amplifier through a wiring.

Signal processing device of touch panel

Signal processing circuit for a capacitive touch panel capable of switching between a differential-input sensor circuit and a single-input sensor circuit

A detection circuit includes: a control signal updating circuit configured to update a digital control signal for controlling drive of a sensor based on a clock having a predetermined frequency; a digital to analog converter configured to convert the digital control signal output from the control signal updating circuit to an analog control signal for driving the sensor; a comparator configured to compare a voltage level of a detection signal from the sensor which changes depending on the analog control signal with a reference voltage having a predetermined voltage level to output a comparison result signal; and a counter configured to count to measure a time period depending on the detection signal based on the comparison result signal output from the comparator and a clock having a predetermined frequency.

Detection circuit

A signal detection circuit of a magnetic sensor includes a differential amplifier to which an output voltage of a detecting coil of the magnetic sensor is applied; a comparator to which the output of the differential amplifier is input, the comparator outputting a digital signal having one logical value during a time period between two adjacent spike voltages included in the output voltage; and a counter that counts the number of pulses of a clock in a period when the output of the comparator has one logical value.

Magnetic sensor signal detection circuit using a counter

An exciting coil drive circuit of a magnetic sensor comprises a D/A converter that receives input of digital data for detecting a magnetic field; a first amplifier that outputs a drive signal P applied to one end of an exciting coil of the magnetic sensor based on the output signal of the D/A converter; and a second amplifier that outputs a drive signal N applied to the other end of the exciting coil based on the output signal of the D/A converter, the drive signal N being an inversion signal of the drive signal P, the drive signal N intersecting with the drive signal P twice or more.

Growing community of inventors

Midori, Japan

Kazuyuki Kobayashi