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Battery-initiated touch-sensitive power-up

  • US 5,249,298 A
  • Filed: 12/28/1992
  • Issued: 09/28/1993
  • Est. Priority Date: 12/09/1988
  • Status: Expired due to Fees
First Claim
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1. A circuit, comprising:

  • (a) first and second power input nodes;

    (b) an output node;

    (c) a sense input node;

    (d) a first switch between said output node and an internal node;

    (e) a comparator with inputs connected to said first and second power input nodes and with output driving a second switch between said internal node and said first power input node, wherein (i) when a voltage at said first power input node exceeds a voltage at said second power input node, said second switch connects said internal node to said first power input node, but (ii) when said voltage at said first power input node is less than said voltage at said second power input node, said second switch disconnects said internal node from said first power input node;

    (f) a detector with input connected to said sense input node and with output driving said first switch, wherein a voltage change at said sense node detected by said detector when said first switch disconnects said internal node from said output node drives said first switch to connect said internal node with said output node; and

    (g) a timer coupled to said detector, said timer starting a time interval when said detector detects said voltage change, wherein said timer at the end of said time interval drives said first switch to disconnect when said comparator drives said second switch to disconnect.

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