A Low-Electromagnetic-Interference Buck Converter With Continuous-Time Delta-Sigma-Modulation and Burst-Mode Techniques

Abstract

This paper presents a high-efficient low-noise buck converter with continuous-time delta-sigma-modulation and burst-mode techniques. The proposed buck converter uses the techniques of over-sampling, noise shaping, burst mode, and continuous-time second-order delta-sigma modulator to achieve low output noise, low overshoot and undershoot voltage, and improve the recovery time. First, the second-order DSM can lower the switching frequency noise, overshoot, and undershoot of the converter. Second, the noise shaping technique can move the noise to high frequency and filter out the noise within bandwidth. Third, the burst-mode technique can accelerate the transient response. The proposed chip is fabricated with a 0.35 μ m Taiwan Semiconductor Manufacturing Company (TSMC) CMOS process and the chip area is 1.5 × 1.5 mm. The transient recovery time is 6 and 16 μ s, when the load current changes from 600 to 50 mA and from 50 to 600 mA, respectively. The output noise spectrum is –67.5 dbm, when output voltage is 2 V. The maximum efficiency is 91.6%, when the output voltage is 2 V. The supply voltage is 3.3 V. The output voltage range of the proposed converter is 1–2.5 V.