US 7,064,534 B2Granted

Regulator circuitry and method

AssigneeSTMicroelectronics S.r.l.

InventorsDavid C. McClure, Mehdi Zamanian

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Abstract

A regulator circuit and method are disclosed for a system. The regulator circuit may include a compare circuit for comparing a first supply voltage to a predetermined voltage level and generating an enable signal based upon the comparison. A selectively enabled voltage regulator is adapted to make available a predetermined current level at a regulated voltage when enabled by the compare circuit. When disabled, the voltage regulator circuit is prohibited from providing current. The voltage regulator may include an output transistor that is normally biased in a saturation mode of operation and is deactivated by the enable signal. By controlling the output transistor based upon the output of the compare circuit, the need for a relatively large transistor for connecting to the first supply voltage is eliminated.

Claims21

Dependent claims

A system, comprising:

a first voltage regulator having a supply input coupled to a common unregulated supply voltage, an enable input and a first supply output, the first voltage regulator selectively providing at the first supply output up to a first predetermined current level at a regulated voltage based upon the common unregulated supply voltage;
compare circuitry having an input coupled to a first unregulated supply voltage and an output having a value indicative of whether the first unregulated supply voltage is greater than a predetermined voltage level;
a second voltage regulator having a supply input coupled to the common unregulated supply voltage, an enable input responsive to the compare circuitry output and a second supply output, the second voltage regulator selectively providing at the second supply output thereof up to a second predetermined current level at a regulated voltage based upon the common unregulated supply voltage, the first supply output of the first voltage regulator being coupled to the second supply output of the second voltage regulator;
and
switching circuitry operable responsive to the output of the compare circuitry for applying either the first unregulated supply voltage or a second unregulated supply voltage as the common unregulated supply voltage.

2 more elements

A device, comprising:

a first voltage regulator having a supply input, an enable input and a supply output, the first voltage regulator receiving a common unregulated supply voltage at the supply input and providing at the supply output a regulated voltage at up to a first predetermined current level when enabled and providing substantially no current when disabled,
a switching circuit for applying either a first unregulated supply voltage or a second unregulated supply voltage as the common unregulated supply voltage, and
a compare circuit having an input adapted to be coupled to the first unregulated supply voltage, for generating a signal at an output of the compare circuit having a value indicative of the first unregulated supply voltage appearing at the input being greater than a predetermined reference voltage, the output of the compare circuit being coupled to the enable input of the first voltage regulator and to control the operation of the switching circuit.

Dependencies are inferred from the claim text.