Sanyo Electric Co., Ltd.

Semiconductor Components Industries, LLC

Sanyo Semiconductor Co., Ltd.

Tatsuya Suzuki

Kazuyuki Kobayashi

Yasuhiro Kaneta

Kumiko Fukai

Takashige Ogata

Shuhei Kawai

Yoshitaka Onaya

Yasuhiro Kaneda

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

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.

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

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

A step down DC-DC converter is reduced in the cost by reducing a number of capacitors included. The DC-DC converter is provided with switches that connect (n&#x2212;1) capacitors in parallel with each other and switches that connect the capacitors in series with each other. In phasesome switches are turned on to connect the capacitors in parallel between an output terminal and a ground voltage so that the capacitors are charged. In phaseother switches are turned on to connect the capacitors in series between the output terminal and an input voltage so that the capacitors are discharged. A stepped down output voltage, that is 1/n times of the input voltage, is obtained by alternating the phaseand the phaseuntil a stable state is reached.

DC-DC converter with switchable capacitors

A driver circuit to obtain a current to drive a light emitting device is reduced in a patterning area and improved in efficiency. A positive power supply voltage Vdd is applied to an anode of a white LED, while a voltage &#x2212;0.5 Vdd from a &#x2212;0.5 Vdd generation circuit is applied to a cathode of the white LED through an N-channel type MOS transistor. The &#x2212;0.5 Vdd generation circuit generates the voltage &#x2212;0.5 Vdd according to a clock &#x3a6; from a clock generation circuit. A voltage of 1.5 Vdd is applied between the anode and the cathode of the white LED, as equivalent to a prior art. Since N-channel type MOS transistors are heavily used in the &#x2212;0.5 Vdd generation circuit, the driver circuit requires less patterning area to obtain the same amount of current to drive the LED as in the prior art. In addition, a parasitic capacitance is reduced to improve efficiency of the driver circuit.

Driver circuit

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.

Exciting coil drive circuit of magnetic sensor

A size of a charge pump circuit is reduced as well as its cost. In a positive booster charge pump circuit in an embodiment of this invention, a positive boosted voltage 2VDD generated at its first stage node is used as a gate voltage to turn on a MOS transistor that outputs a high level (VDD) of each of the first, third and fourth clock drivers. And in a negative charge pump circuit, a negative boosted voltage &#x2212;VDD generated at its first stage node is used as a gate voltage to turn on a MOS transistor that outputs a high level of each of the second and fifth clock drivers.

Charge pump circuit

A reverse current is prevented in a charge pump circuit. A complementary pair of clocks CLK and *CLK varies while a first through a fourth charge transfer MOS transistors MMMand Mare turned off. Then the second charge transfer MOS transistor Mis turned on to discharge a first pumping capacitor CA and the third charge transfer MOS transistor Mis turned on to charge a second pumping capacitor CB. Next, the complementary pair of clocks CLK and *CLK varies after the first through the fourth charge transfer MOS transistors MMMand Mare turned off again. Then the fourth charge transfer MOS transistor Mis turned on to discharge the second pumping capacitor CB and the first charge transfer MOS transistor Mis turned on to charge the first pumping capacitor CA.

Growing community of inventors

Kumagaya, Japan

Tatsuya Suzuki