Sensor output circuit

• US 8,397,571 B2
• Filed: 05/17/2010
• Issued: 03/19/2013
• Est. Priority Date: 06/01/2009
• Status: Expired due to Fees

• Current Assignee: North Star Innovations Inc. (Wi-LAN Inc.)
• Original Assignee: Freescale Semiconductor, Inc. (NXP Semiconductors NV)
• Inventors: Murayama, Katashi
• Primary Examiner(s): Kwok, Helen C.
• Application Number:
  US12/781,796
• Publication Number:
  US 20100301937A1
• Time in Patent Office: 1,037 Days
• Field of Search: 735/10, 734/97, 73/13.8, 73/18.8, 735/141.6, 734/95, 702/104
• US Class Current: 73/510
• CPC Class Codes: H03F 2200/447 the amplifier being protected to temperature influence
• CPC Class Codes: H03F 2203/45512 the FBC comprising one or more capacitors, not being switched capacitors, and being coupled between the LC and the IC
• CPC Class Codes: H03F 2203/45514 the FBC comprising one or more switched capacitors, and being coupled between the LC and the IC
• CPC Class Codes: H03F 2203/45586 the IC comprising offset generating means
• CPC Class Codes: H03F 2203/45588 the IC comprising offset compensating means
• CPC Class Codes: H03F 3/005 using switched capacitors, e.g. dynamic amplifiers; using switched capacitors as resistors in differential amplifiers H03F3/45 takes precedence
• CPC Class Codes: H03F 3/45475 using IC blocks as the active amplifying circuit
• CPC Class Codes: H03F 3/45928 using IC blocks as the active amplifying circuit

Abstract

An output circuit that occupies a small area includes a control unit, X, Y, and Z axes amplification units, and first and second common circuits. The control unit outputs a temperature coefficient offset for correcting the temperature dependence of a sensor output. The first and second common circuits use the output from an acceleration sensor when performed amplification for each axis. In a reset phase, the charge accumulated in the first and second common circuits is released. In an amplification phase, the first and second common circuits and an operational amplifier uses the temperature coefficient offset voltage of each voltage to correct and amplify a signal from the acceleration sensor. In a hold phase, the accumulated charge is maintained in the same state to hold the output value of each axis.

Claims

1. An output circuit, comprising:

a first capacitor sequentially provided with sensor measurement signals from a plurality of sensors;

a differential amplification circuit arranged for each sensor and including a first terminal, which receives a voltage of the first capacitor, and a second terminal, which receives a reference voltage for correcting the sensor measurement signals;

a hold capacitor arranged in each differential amplification circuit between an output terminal and the first terminal;

a correction coefficient generation circuit that sequentially provides correction coefficients for correcting the sensor measurement signals of the sensors;

a second capacitor that accumulates the correction coefficients from the correction coefficient generation circuit and provides the correction coefficients to the second terminal of the differential amplification circuit; and

a first switch circuit that connects the second capacitor to each differential amplification circuit in synchronism with the sensor measurement signals.

2. The output circuit of claim 1, wherein the first switch circuit executes a reset phase to short circuit two ends of the second capacitor before connecting the second capacitor to each differential amplification circuit.

3. The output circuit of claim 2, further comprising:

a second switch circuit arranged in each differential amplification circuit to connect a third capacitor between the output terminal and the first terminal;

wherein the second switch circuit connects the third capacitor to each differential amplification circuit in synchronism with the sensor measurement signals.

4. The output circuit of claim 3, wherein the second switch circuit short circuits two ends of the third capacitor in the reset phase.

5. The output circuit of claim 1, wherein the first capacitor is connected to an acceleration sensor that measures acceleration for a plurality of axes, and obtains from the acceleration sensor a signal that arranges acceleration detection signals for each axis in chronological order as the sensor measurement signals.