Coded data generation or conversion – Analog to or from digital conversion – Analog to digital conversion
Patent
1997-09-17
2000-01-11
Williams, Howard L.
Coded data generation or conversion
Analog to or from digital conversion
Analog to digital conversion
341156, H03M 114
Patent
active
060140984
ABSTRACT:
The output of each cell in an A-D converter on an IC chip is dependent upon the relative values of an input voltage and an individual one of progressive fractions of a reference voltage respectively introduced to the branches in a differential amplifier. To minimize output errors from cell mismatches, first and second sets of averaging impedances, preferably resistors, are respectively connected between the output terminals in the first branches, and the output terminals in the second branches, in successive pairs of cells. The impedances have relatively low values, particularly compared to the impedances of current sources connected to the branch output terminals. First and second resistive strips on the chip may be tapped at progressive positions to respectively define the impedances in the first and second sets. One end of each strip may be connected to the opposite end of the other strip to define a closed impedance loop for minimizing averaging errors at the strip ends. Different fractions of the reference voltage are associated with each individual impedance in the first and second sets. Such reference voltage fractions have a particular repetitive relationship. In this way, the number of output terminals is reduced and cell mismatches are reduced. The different outputs at each individual impedance are determined for the progressive fractions of the reference voltage at such impedance. Successive voltage fractions for each impedance have opposite polarities to provide a folding relationship. Such outputs may be cascaded to further reduce cell mismatches and the number of output terminals.
REFERENCES:
patent: 5157397 (1992-10-01), Vernon
patent: 5856800 (1999-01-01), Le Pailleur et al.
Buchwald Aaron W.
Bult Klaas
Broadcom Corporation
Williams Howard L.
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