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Processor supervisory circuit and method having increased range of power-on reset signal stability
| Details |
Inventors: Wittman, Brian Albert;
Assignee: Lucent Technologies Inc. (Murray Hill, NJ)
Primary Examiner: Callahan; Timothy P.
Assistant Examiner: Kim; Jung Ho
Attorney, Agent or Firm:
For use in a processor supervisory circuit, a power-on reset circuit, a method of producing a power-on reset ("RESET") signal and a power supply including the circuit. The circuit includes: (1) an adaptive, nonlinear voltage divider having a voltage input and a voltage output, the divider dividing an unscaled, unregulated voltage received at the voltage input by a factor that varies a function of the unscaled, unregulated voltage to produce a scaled, unregulated voltage at the voltage output and (2) a comparison circuit for comparing the scaled, unregulated voltage with a scaled, regulated voltage to produce the RESET signal when the scaled, regulated voltage exceeds the scaled, unregulated voltage, the divider being adaptive and nonlinear to ensure that the comparison circuit continuously produces the RESET signal when the scaled, regulated voltage exceeds the scaled, unregulated voltage and thereby avoid premature activation of a processor couplable to the power-on reset circuit. |
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DETAILED DESCRIPTION To address the above-discussed deficiencies of the prior art, the present invention provides a novel, low-cost, discrete-component processor supervisory circuit.
More specifically, the present invention provides, for use in a processor supervisory circuit, a power-on reset circuit, a method of producing a power-on reset ("RESET") signal and a power supply including the circuit.
The circuit includes: (1) an adaptive, nonlinear voltage divider having a voltage input and a voltage output, the divider dividing an unscaled, unregulated voltage received at the voltage input by a factor that varies as a function of the unscaled, unregulated voltage to produce a scaled, unregulated voltage at the voltage output and (2) a comparison circuit for comparing the scaled, unregulated voltage with a scaled, regulated voltage to produce the RESET signal when the scaled, regulated voltage exceeds the scaled, unregulated voltage, the divider being adaptive and nonlinear to ensure that the comparison circuit continuously produces the RESET signal when the scaled, regulated voltage exceeds the scaled, unregulated voltage and thereby avoid premature activation of a processor couplable to the power-on reset circuit.
The present invention introduces a processor supervisory circuit that avoids instabilities at low voltages by providing a nonlinear voltage divider to scale input voltages by a factor that varies as a function of the values of the voltages.
This ensures that, at low input voltages, conditions that could cause deassertion of the reset signal cannot exist.
In one embodiment of the present invention, the divider comprises a switch, activatable as a function of the unscaled, unregulated voltage, to introduce an additional resistive element into the divider to change the factor.
Of course, resistances or, more broadly, impedances, may be introduced into or removed from the divider to change the factor by which it divides the unscaled, unregulated voltage.
Further, those of ordinary skill in the art are familiar with other ways of scaling voltages using pulse-width modulation or the like
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I/O Systems 
