Current sensing circuit for DC/DC buck converters

摘要

A circuit (20) and a related method to sense the inductor current (IL) of DC/DC buck converters have been achieved. The inductor current (IL) is sensed by generation of a voltage drop across a fully integrated sense resistor (23). The voltage drop is proportional to the inductor current (IL) in the pass device (21) by supplying a fraction of the inductor current (IL) out of a source-follower (22), which matches to the pass device (21). The source of said source-follower (22) is connected to a sense-resistor (23) that is connected to the same supply (VDD) as the pass device (21). The current, which is needed to generate the voltage drop, is fed back into the inductor current (IL) minimizing therefore the efficiency loss. Mirroring, amplification and offset correction of the voltage drop across the sense-resistor (23) is performed by using a single matching pair of source-follower (25,26), which is supplied by a current (IREF) tracking the internal reference voltage and the process variations of the resistors. <IMAGE>