Low power voltage regulator with improved on-chip noise isolation

Abstract

A voltage regulator for isolating radio frequency circuits from on chip digital circuit originated noise and an integrated circuit chip including the voltage regulator. The voltage regulator includes regulator device (a PFET) driven by a sense amplifier to derive a regulator voltage from a supply voltage . Another sense amplifier senses changes in output load and adjusts current flow through a current shunt so that the current shunt shunts excess load current. The sense amplifier driving the voltage regulator device senses current flow through the current shunt and adjusts the current supplied by the regulator device to reduce excess current. The current shunt is a series connected PFET and NFET diode , with the gate of the PFET driven to control current flow. Each of the sense amplifiers includes a pair of PFETs and a pair of NFETs , the drain of each PFET of the pair is tied to a corresponding drain of one of the pair of NFETs. A voltage divider connected between the regulator voltage and ground provides a sense voltage to the output sense amplifier so that the output sense amplifier compares the sense voltage against a reference voltage (VREF) to determine whether the regulator device is providing too much, not enough or just the right output current level.