A Precise Sub-milliohm DCR Current Sensing Scheme for Area-Efficient Multiphase Peak Current Mode Controller

摘要

This paper proposes a low direct current resistance (DCR) current sensing scheme for multiphase peak current mode controller. A second order RC sensing network amplifies the high frequency sensing signal and also extracts the low frequency signal. The sensing error of traditional DCR current sensing, which caused by the input bias current of the sensing circuit, is cancelled. A time-shared amplifier amplifies the low frequency signals from all the phases, and the outputs are combined with the exaggerated high frequency signals of each phase respectively to rebuild the current sensing signals. Small signal analysis and the design guidelines of the proposed sensing scheme are presented. The proposed method enhances the signal-to-noise ratio of traditional DCR current sensing, improves the phase to phase current balancing and dramatically reduces silicon area of the sensing circuit. The experimental results on the fabricated IC controller show that the controller provides small PWM jittering, tight current balancing and fast dynamic response.