Coded data generation or conversion – Analog to or from digital conversion – Analog to digital conversion
Patent
1994-12-06
1997-02-25
Gaffin, Jeffrey A.
Coded data generation or conversion
Analog to or from digital conversion
Analog to digital conversion
341118, 341165, H03M 138
Patent
active
056063202
ABSTRACT:
A micropower analog-to-digital converter (ADC) for use in an implantable medical device is disclosed. The ADC achieves a high conversion speed at micropower levels through a number of timing and circuit improvements over the conventional implementation of the successive approximation ADC architecture. The ADC includes a digital-to-analog converter (DAC) that preferably is implemented as a binary-weighted, switched capacitor array that employs top plate charging and performs bipolar conversion. The DAC provides an analog output signal representing array charge to a comparator. During a comparator latch phase, the DAC asynchronously determines a bit of the ADC digital output signal in response to the comparator output, and initiates a test of the next least significant bit during the same latch phase. Further, the DAC analog output signal is timed to settle during the latch phase in response to both the bit update and the next bit test. In conjunction with increasing conversion speed, the DAC reduces power requirements by using a power gated buffer that selectively increases the power of the ADC input signal only when necessary to drive the ADC conversion circuitry. Further, the comparator includes a precharged static memory cell to avoid crossover currents. Finally, the ADC includes a digital offset correction DAC that corrects not only the cumulative offset voltage generated by components of the ADC, but also the offset voltage of any device that provides the ADC input.
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Gordon, Bernard M., "Linear Electronic Analog/Digital Conversion Architectures, Their Origins, Parameters, Limitations, and Applications," Data Conversion Integrated Circuits, IEEE Press (New York 1980), pp. 32-68.
Zuch, Eugene L., "Principles of Data Acquisition and Conversion," Data Acquisition and Conversion Handbook, DATEL (Massachusetts 1979).
Gaffin Jeffrey A.
Kost Jason L. W.
Pacesetter Inc.
Weinberg Lisa P.
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