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Start up circuit and current-foldback protection for voltage regulators

  • US 5,666,044 A
  • Filed: 09/27/1996
  • Issued: 09/09/1997
  • Est. Priority Date: 09/29/1995
  • Status: Expired due to Term
First Claim
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1. A circuit, connectable to a pass transistor for starting-up and limiting pass current in the pass transistor, having an output terminal with an output voltage, the circuit comprising:

  • a start-up circuit to provide a start-up signal and a foldback signal, wherein the start-up signal and the foldback signal are responsive to a start-up control signal;

    an output stage circuit, having an input terminal with an input voltage, responsive to the start-up signal, to control the pass current in response to the input voltage when the pass transistor is coupled to the output stage circuit;

    a signal generator circuit, coupled to the output voltage terminal, to provide a current limit signal and the start-up control signal, wherein the current limit signal and the start-up control signal are responsive to the output voltage; and

    a current limit amplifier responsive to a current sense signal and a limit signal, and coupled to the input terminal of the output stage to limit the pass current from exceeding a current limit threshold, where the current sense signal is indicative of the pass current and the limit signal is responsive to the foldback signal and the current limit signal.

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