Active Sensing Element for Acoustic Imaging Systems
First Claim
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1. An acoustic imaging sensor comprising:
- a high voltage node;
a low voltage node;
an acoustic element in communication with a bottom surface of a substrate, configured to produce an acoustic input into the substrate, the acoustic element comprising;
an ultrasonic transducer;
a drive circuit configured to couple the ultrasonic transducer to the high voltage node and generate the acoustic input; and
a sense circuit coupled to the low voltage node and configured to obtain an acoustic output from the substrate; and
a controller configured to increase a voltage bias of the sense circuit when the drive circuit is active.
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Abstract
An acoustic fingerprint imaging system having a plurality of acoustic elements, each acoustic element including a transducer, and independent drive and sense circuitry is disclosed. Drive circuitry may require higher voltage than low voltage sense circuitry. Many embodiments described herein include a ground shifting controller to apply a voltage bias to the low voltage sense circuitry during a drive operation, in order to prevent electrical damage to the sense circuitry.
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Citations
22 Claims
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1. An acoustic imaging sensor comprising:
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a high voltage node; a low voltage node; an acoustic element in communication with a bottom surface of a substrate, configured to produce an acoustic input into the substrate, the acoustic element comprising; an ultrasonic transducer; a drive circuit configured to couple the ultrasonic transducer to the high voltage node and generate the acoustic input; and a sense circuit coupled to the low voltage node and configured to obtain an acoustic output from the substrate; and a controller configured to increase a voltage bias of the sense circuit when the drive circuit is active. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A method of driving an acoustic element comprising a high voltage drive circuit and a low voltage sense circuit, the method comprising:
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increasing a voltage bias of the low voltage sense circuit such that the potential difference between a voltage source of the low voltage sense circuit and a circuit ground of the low voltage sense circuit does not exceed a selected threshold; and applying a high voltage drive signal to an ultrasonic transducer coupled to the high voltage drive circuit. - View Dependent Claims (13, 14, 15, 16, 17, 18)
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19. A method of reading an output of an acoustic element of an acoustic fingerprint imaging system comprising a high voltage drive circuit and a low voltage sense circuit, the method comprising:
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removing a voltage bias of the low voltage sense circuit such that the potential difference between a voltage source of the low voltage sense circuit and a circuit ground of the low voltage sense circuit does not exceed a selected threshold; decreasing a voltage bias of the high voltage drive circuit such that the potential difference between a voltage source of the high voltage drive circuit and a circuit ground of the high voltage drive circuit is approximately zero volts; applying a reset voltage signal to the low voltage sense circuit; and measuring a voltage output from the low voltage sense circuit. - View Dependent Claims (20, 21, 22)
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Specification