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Data-directed scrambler for multi-bit noise shaping D/A converters

  • US 5,404,142 A
  • Filed: 08/05/1993
  • Issued: 04/04/1995
  • Est. Priority Date: 08/05/1993
  • Status: Expired due to Term
First Claim
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1. For use in apparatus for converting digital signals to analog signals, wherein a multi-bit digital signal is transformed to a thermometer code which passes through a scrambler to a D/A converter to produce an analog output signal;

  • an improved scrambler comprising;

    input means and output means;

    a plurality of switchable scrambler devices configured as swapper cells interconnected to provide a number of mutually-exclusive selectable signal paths from said input means to said output means;

    each of said swapper cells including;

    two input terminals to receive respective signal bits and two output terminals to produce corresponding output bits;

    means within each swapper cell for controllably connecting the two input terminals to the two output terminals either directly or reversely;

    select terminal means for receiving an activating signal designating whether the swapper cell is to effect said direct connection or said reverse connection;

    logic means for producing said activating signal;

    said logic means including means for storing the integrated difference of past swapper output signals;

    said logic means further including means for computing the new value of the activating signal based on the current two input values to said swapper cell and said stored integrated difference signal and for updating the value of the stored difference signal.

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