A Mixed-Signal Adaptive Ripple Canceler for Switching Regulators Providing 18 dB-24 dB of Ripple Rejection up to 1 MHz

A mixed-signal adaptive ripple canceller for reducing switching noise and spurious emissions in switching regulators is presented. The proposed mixed-signal ripple suppression technique tracks and cancels the switching noise by utilizing two schemes: A primary mixed-signal adaptive ripple canceller that provides large signal ripple cancellation up to 20 dB, and an auxiliary linear amplifier-based ripple canceller that minimizes the residual ripple content, achieving a combined ripple rejection of 24 dB. Proposed approach operates without the need for external components, reducing overall printed circuit board area without loss of efficiency. The adaptive ripple canceller is designed and fabricated in a 250 nm CMOS process with four levels of metal. The ripple-canceller is integrated with an on-chip buck regulator to characterize its rejection effectiveness. The ripple canceller can also be utilized as a stand-alone ripple cleaner module with an external commercial-off-the-shelf (COTS) switching regulator. The proposed ripple canceller can track and cancel power supply ripple up to 1 MHz with 24 dB rejection and reduces ripple content up to fourth harmonic by at least 20 dB while supporting dc loads up to 1 A and ripple currents up to 350 mApk-pk. The proposed approach achieves 30% lower quiescent current than using a linear low-dropout regulator without the need for any external components.