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Soft-start reference ramp and filter circuit

  • US 7,573,252 B1
  • Filed: 06/07/2004
  • Issued: 08/11/2009
  • Est. Priority Date: 06/07/2004
  • Status: Active Grant
First Claim
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1. A circuit for providing controlled ramping and filtering, comprising:

  • a voltage regulator controller, including;

    a current mirror circuit that is arranged to receive a reference voltage and to provide a charging current from a biasing current, wherein the current mirror circuit includes a first and a second transistor having sources receiving said reference voltage;

    a soft-start capacitor circuit that is arranged to provide a conditioned reference voltage based, in part, on the charging current, wherein the soft-start capacitor circuit is coupled to the second transistor, and wherein the soft-start capacitor circuit is arranged such that the conditioned reference voltage is substantially stable during a steady state and such that the conditioned reference voltage substantially tracks the reference voltage during the steady state;

    a switch circuit comprising a transistor, wherein the switch circuit is arranged to receive a switch control signal, and wherein the switch circuit is arranged to shunt the charging current away from the soft-start capacitor circuit, if the switch control signal corresponds to an inactive level, and further arranged to enable the soft-start capacitor circuit to be charged, if the switch control signal corresponds to an active level; and

    a differential amplifier that is arranged to receive a feedback voltage that is based at least, in part, on a regulated output voltage;

    to receive the conditioned reference voltage;

    and to, during all operating states, compare the conditioned reference voltage with the feedback voltage.

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