Voltage supervisory circuit for a multi-rail power supply
AssigneeHewlett-Packard Company
InventorStephen Ejner Horvath
Life of this patent
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Abstract
An apparatus for supervising input voltages of a multi-rail power supply includes a corresponding voltage detector unit electrically connected to each rail for ascertaining values of the input voltages of each rail. An output of each voltage detector unit is electrically connected at a wired-or node. A pull-up resistor is connected between the wired-or node and a power supply for pulling the voltage level of the wired-or node high. Circuitry generates a power-good signal responsive to the voltage of the wired-or node being greater than a predetermined threshold voltage.
Claims17
Apparatus for supervising at least two input voltages supplied thereto, said apparatus comprising:
- voltage detector means corresponding to each of the at least two input voltages for receiving the at least two input voltages and ascertaining corresponding values of the at least two input voltages;
- a wired-or node electrically connected to outputs of said corresponding voltage detector means;
- pull-up means adapted to be electrically connected to a power supply and connected to said wired-or node for pulling a voltage level of said wired-or node high when each of said corresponding values of the at least two input voltages exceeds a predetermined threshold voltage of said corresponding voltage detector means;
- means for generating a power-good signal responsive to said voltage level of said wired-or node being high;
- and
- a delay circuit including a resistor and a capacitor connected in series between said wired-or node and ground, respectively, for delaying generation of said power-good signal for a predetermined time.
Apparatus for generating a power-good signal from at least two input voltages supplied to said apparatus, said apparatus comprising:
- voltage detector means corresponding to each of the at least two input for receiving the at least two input voltages and ascertaining whether each of the at least two input voltages exceeds a predetermined threshold voltage of said corresponding voltage detector means;
- a wired-or node electrically connected to outputs of said corresponding voltage detector means for holding a signal for producing the power-good signal when said corresponding voltage detector means indicate that each of the at least two input voltages has exceeded said predetermined threshold voltage of said corresponding voltage detector means;
- a delay circuit including a resistor and a capacitor connected in series between said wired-or node and ground, respectively, for delaying generation of the power-good signal for a predetermined time after said wired-or node holds said signal for producing the power-good signal;
- and
- discharge means electrically connected to said delay circuit and said wired-or node for rapidly discharging said delay circuit when any of the at least two input voltages falls below said predetermined threshold voltage of said corresponding voltage detector means for a shorter period of time than would otherwise be required to discharge said delay circuit.
Dependencies are inferred from the claim text.