A noise-shaped buck DC-DC converter based on a 3rd-order continuous-time active-passive sigma-delta modulator

A noise-shaped synchronous buck converter using a 3
^rd
-order continuous-time (CT) active-passive sigma-delta modulator (SDM) is presented. Detailed system modeling and loop design methodology for the SDM based DC-DC are discussed. The proposed circuit has been designed with Chartered 0.35 µm CMOS process. The system operates with a clock of 8 MHz. Compared with the traditional PWM mode converter, simulation results show that the proposed converter suppresses the switching tones by more than 25 dB over a wide frequency range with a peak efficiency of 96%.