Low voltage current monitoring circuit

Abstract

A current monitor () having a high performance, simple, and cost effective design that is independent of process, temperature and voltage is disclosed herein. The current monitor () includes a sensing transistor () that couples to the main transistor () of an adjoining voltage regulator. Specifically, the control and source nodes of each transistor couple to each other, respectively. The size of the main transistor () is a predetermined multiple integer n of the size of the sensing transistor. A first resistor (R) couples between a supply voltage and the drain node of the main transistor (). A second resistor (R) couples between a supply voltage and the drain node of the sensing transistor (), wherein the size of the second resistor (R) is equal to the size of the first resistor (R) multiplied by the predetermined multiple integer n. An inverting input of an amplifier () couples to the drain node of the sensing transistor (), while a third resistor (R) connects between the supply voltage and a non-inverting input of the amplifier (). The amplifier () drives a transistor () within a closed feedback loop to equalize the value of the voltages at both inputs of the amplifier (). A feedback resistor (R) coupled between the source node of the transistor () and ground. A comparator () connects to the source node of the transistor () and between a current source and a reference resistor (R) to provide an output voltage.