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Multistep analog-to-digital converter with embedded correction data memory for trimming resistor ladders

  • US 5,218,362 A
  • Filed: 07/02/1992
  • Issued: 06/08/1993
  • Est. Priority Date: 07/02/1992
  • Status: Expired due to Term
First Claim
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1. An analog-to-digital converter, comprising:

  • an input circuit that receives an input signal having an input voltage;

    a resistor ladder circuit that generates a sequence of N stepped reference voltages, where N is an integer larger than four;

    M comparator circuits that simultaneously compare said input voltage with M of said N stepped reference voltages and generate M binary comparison signals, wherein M≦

    N and said M comparator circuits are coupled to said input circuit and said resistor ladder;

    a digital encoder, coupled to said M comparator circuits, that encodes said M binary comparison signals to generate a multiple-bit first digital conversion value;

    a programmable memory that stores a multiplicity of digital correction values, wherein said programmable memory is addressed by at least a subset of said first digital conversion value'"'"'s most significant bits and outputs a corresponding one of said multiplicity of digital correction values;

    a digital-to-analog converter that converts said digital correction value output by said programmable memory into an analog correction voltage;

    a circuit for generating a residual voltage corresponding to a selected one of said N stepped reference voltages, corresponding to said first digital conversion value, minus said input voltage, plus an offset voltage proportional to said analog correction voltage; and

    means for converting said residual voltage into a second digital conversion value.

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