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Apparatus and method for selectively driving a piezo transducer

  • US 8,525,685 B2
  • Filed: 05/27/2010
  • Issued: 09/03/2013
  • Est. Priority Date: 11/29/2007
  • Status: Active Grant
First Claim
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1. An apparatus for controlling a device having a touch sensor, comprising:

  • a piezo transducer for detecting a pressure pattern applied to the sensor;

    a comparator coupled to the transducer; and

    a pressure pattern recognition circuit coupled to a comparator output of the comparator, the circuit being configured to;

    determine whether the pressure pattern satisfies a predetermined condition; and

    in response to the pressure pattern satisfying the predetermined condition, generate an output signal;

    a switch coupled to and selectively connecting the transducer to one of (i) a logic circuit and (ii) an oscillator, wherein;

    the transducer operates as a pressure pattern detector in response to being connected to the logic circuit, wherein the logic circuit provides a signal value corresponding to a logic value, thereby grounding a bottom lead of the transducer; and

    the oscillator provides an oscillating signal, thereby increasing a drive voltage to the transducer; and

    the transducer operates as an alarm generator in response to being connected to the oscillator;

    an inverter connected between the switch and a bottom lead of the transducer, wherein;

    the inverter is configured to transmit a ground signal to the transducer to permit the transducer to operate as the pressure pattern detector; and

    the inverter is configured to transmit an oscillating signal to the transducer to permit the transducer to operate as the alarm generator;

    a tri-state buffer coupled to a top lead of the transducer, wherein;

    in response to the tri-state buffer being set to a high impedance state, the transducer is permitted to operate as the pressure pattern detector; and

    in response to the tri-state buffer being set to a low impedance state, the transducer is permitted to operate as the alarm generator.

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