Patent ID: 8624568

Claim:
Voltage regulator circuitry comprising: (a) a differential input stage including a first input coupled to receive a reference voltage, a second input coupled to a regulated output conductor of the voltage regulator circuitry, and an output; (b) an output stage for producing a regulated output voltage on the regulated output conductor, including 1) a transient pull-up transistor having a first electrode coupled to a first supply voltage and a second electrode coupled to the regulated output conductor, a transient pull-down transistor having a first electrode coupled to a second supply voltage and a second electrode coupled to the regulated output conductor, 2) a primary pull-up transistor having a first electrode coupled to the first supply voltage and a second electrode coupled to the regulated output conductor, a primary pull-down transistor having a first electrode coupled to the second supply voltage and a second electrode coupled to the regulated output conductor, and 3) a filtering resistor coupled between the regulated output conductor and the second electrodes of the primary pull-up transistor and the primary pull-down transistor; and (c) a gain stage including 1) a cascode transistor having a first electrode coupled to control electrodes of the primary pull-down transistor and the transient pull-down transistor and a second electrode coupled to control electrodes of the primary pull-up transistor and the transient pull-up transistor, and 2) a follower transistor having a first electrode coupled to the regulated output conductor, a control electrode coupled to the output of the differential input stage, and a second electrode coupled to the first electrode of the cascode transistor and the control electrodes of the primary pull-down transistor and the transient pull-down transistor, wherein the differential input stage, output stage, and gain stage operate to 1) regulate the output voltage to a predetermined value having a predetermined relationship to the regulated output voltage by controlling the primary pull-up transistor and the primary pull-down transistor during normal voltage regulating operation, and 2) turn on the transient pull-up transistor or the transient pull-down transistor in response to a sufficiently large, fast transition of a load current flowing in the regulated output conductor, depending on the direction of the transition of the load current, so as to cause rapid settling of the regulated output voltage back to the predetermined value.