Apparatus and method for reducing noise in fingerprint sensing circuits
First Claim
1. An apparatus for reducing noise in fingerprint sensing circuits, the apparatus comprising:
- a fingerprint sensing area onto which a user can apply a finger;
an analog front end coupled to the fingerprint sensing area to generate an analog response signal;
an analog-to-digital converter (ADC) to sample the analog response signal and convert the sample to a digital value; and
a digital device configured to receive the digital value from the ADC, the digital device further configured to operate while the ADC is converting sampled analog response signals to digital values and to shut down while the ADC is sampling the analog response signals.
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Abstract
An apparatus for reducing noise in fingerprint sensing circuits is disclosed in one embodiment of the invention as including a fingerprint sensing area onto which a user can apply a fingerprint. An analog front end is coupled to the fingerprint sensing area and is configured to generate an analog response signal. An analog-to-digital converter (ADC) samples the analog response signal and converts the sample to a digital value, which may be received by a digital device such as a processor or CPU. To reduce the amount of the noise that is present in the analog response signal and therefore reflected in the digital value, the digital device may be shut down while the ADC is sampling the analog response signal.
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Citations
32 Claims
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1. An apparatus for reducing noise in fingerprint sensing circuits, the apparatus comprising:
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a fingerprint sensing area onto which a user can apply a finger; an analog front end coupled to the fingerprint sensing area to generate an analog response signal; an analog-to-digital converter (ADC) to sample the analog response signal and convert the sample to a digital value; and a digital device configured to receive the digital value from the ADC, the digital device further configured to operate while the ADC is converting sampled analog response signals to digital values and to shut down while the ADC is sampling the analog response signals. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 27, 28)
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10. A method for reducing noise in fingerprint sensing circuits, the method comprising:
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providing a fingerprint sensing area onto or over which a user can apply a finger; generating an analog response signal associated with a finger applied onto or over the fingerprint sensing area; sampling the analog response signal; converting the sample to a digital value; receiving the digital value at a digital device; and operating digital circuitry coupled to the sensing circuit while converting the sample to a digital value and shutting down the digital circuitry while sampling the analog response signal. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17, 18)
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19. A method for reducing noise in biometric sensing circuits, the method comprising:
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providing a biometric sensing area on or over which a user can place or swipe a biometric; generating an analog sensor response signal associated with the biometric on or over the fingerprint sensing area; sampling the analog sensor response signal to obtain a sampled analog response signal; converting the sampled analog response signal to a digital value; receiving the digital value at a CPU coupled to the biometric sensing circuit; and operating the CPU while converting a sampled analog response signal to a digital value and turning off the CPU while sampling the analog sensor response signal. - View Dependent Claims (20, 21, 22)
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23. A method for reducing noise in an image sensing circuit comprising:
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sensing an image of an object comprising pixel locations in the image sensing circuit providing an analog output value for each pixel during a respective pixel sample and convert clock time period; sampling the analog output value during an analog sampling portion of the sample and convert clock time period to create a sampled analog signal; converting a sampled analog signal created during a previous sample and convert clock time period to a sampled digital signal during a digital conversion portion of the sample and convert clock time period; and not operating digital circuitry coupled to the sensing circuit during the analog sampling portion and operating digital circuitry during at least a portion of the remainder of the pixel sample and convert clock time period. - View Dependent Claims (24, 25, 26)
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29. An object image sensor comprising:
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an object image sensing device configured to sense pixel locations of an object image each during a respective pixel sample and convert clock time period; an analog signal sampler coupled to the object image sensing device configured to sample a pixel location analog signal from the pixel location during a sample portion of the pixel sample and convert clock time period to create a sampled analog pixel signal and an analog signal converter coupled to the analog signal sampler configured to convert a sampled analog pixel signal sampled during a prior pixel sample and convert clock period to a digital pixel location signal during a conversion portion of the pixel sample and convert clock time period; a digital signal processor, coupled to at least one of the analog signal sampler and analog signal converter, shut off during the sample portion of the pixel sample and convert clock time period and configured to perform at least one of receiving, storing and processing of at least one converted digital pixel location signal, during the remainder of the pixel sample and convert clock period. - View Dependent Claims (30, 31)
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32. A non-transitory machine readable medium storing software which, when executed by a computing device, causes the computing device to perform a method, the method comprising:
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sensing an image of an object comprising pixel locations in the image using a sensor providing an analog output value for each pixel during a respective pixel sample and convert clock time period; sampling the analog output value during an analog sampling portion of the sample and convert clock time period to create a sampled analog signal; converting a sampled analog signal created during a previous sample and convert clock time period to a sampled digital signal during a digital conversion portion of the sample and convert clock time period; and not operating digital circuitry coupled to the sensor during the analog sampling portion and operating digital circuitry during at least a portion of the remainder of the pixel sample and convert clock time period.
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Specification