Low Current DC-DC Converter With Integrated Low Current Coulomb Counter

A power supply system includes a regulator circuit responsive to an input signal at the input node (VIN) for producing an output signal at the output node (VOUT) at a desired level. The regulator circuit has a controller (12), an inductive element (L) and a first switch coupled to the inductor element (A) and controlled by the controller to produce the output signal. Also, the power supply system includes a Coulomb counter (22) for producing a Coulomb count signal proportional to the number of Coulombs passing from the input node to the output node. The Coulomb counter is enabled by an enabling signal representing a predetermined time period, for determining the number of Coulombs passing from the input node to the output node during that predetermined time period.