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Noise tolerant code setting circuit

  • US 5,446,402 A
  • Filed: 08/30/1994
  • Issued: 08/29/1995
  • Est. Priority Date: 09/01/1993
  • Status: Expired due to Fees
First Claim
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1. A code setting circuit comprising:

  • a plurality of pad terminals to each of which a voltage pulse is applied;

    a plurality of thin-film resistors corresponding respectively to the pad terminals, each of said thin-film resistors being connected between the corresponding pad terminal and a reference potential;

    a plurality of first transistors of first conductivity type adapted to be rendered conductive in response to a turn-on pulse;

    a plurality of second transistors of the first conductivity type corresponding to said first transistors, each of the second transistors having a channel connected in parallel with a channel of the corresponding first transistor between a voltage source and a corresponding one of a plurality of nodes;

    a plurality of inverters corresponding respectively to the second transistors and the nodes, each of the inverters being connected between the corresponding node and the gate terminal of the corresponding second transistor;

    a plurality of third transistors of second conductivity type opposite to the first conductivity type and corresponding respectively to said nodes, each of the third transistors having a channel connected at one end to the corresponding node and a gate terminal biased so that the third transistor prevents said voltage source from being coupled through a corresponding one of the second transistors to a corresponding one of said pad terminals;

    a plurality of blocking means respectively corresponding to said third transistors and said pad terminals, each of the blocking means being connected between the other end of the channel of the corresponding third transistor and the corresponding pad terminal for preventing a noise pulse which is generated when said voltage pulse is applied to the corresponding pad terminal from being applied to the corresponding third transistor; and

    means for generating a digital signal corresponding to a set of different potentials developed at said nodes.

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