A 10-μ s Transient Recovery Time Low-EMI DC-DC Buck Converter With Δ - Δ Modulator

This paper presents a 10- $\mu \text{s}$ transient recovery time and a low electromagnetic interference dc–dc buck converter with a second-order delta–sigma ( $\Delta $ – $\Sigma )$ modulator. The proposed buck converter employs the techniques of oversampling, noise shaping, fast-transient path, mode selector, and second-order $\Delta $ – $\Sigma $ modulator to achieve spur reduction and to improve transient recovery time. As a result, the noise tones of the output voltage are less than the other conventional pulsewidth modulation converters. In addition, the fast-transient path could correct output voltage immediately, and the mode selector controls the duty cycle of the converter to limit overshoot voltage and undershoot voltage. The chip was implemented using a 0.35- $\mu \text{m}$ Taiwan Semiconductor Manufacturing Company CMOS process. The measured results show that the transient recovery time is 10 $\mu \text{s}$ from heavy load to light load and from light load to heavy load, and the noise power spectrum demonstrates a −64-dBm peak noise when the output voltage is 2 V and the output current is 300 mA. A maximum efficiency of 89% is measured at 3 V output voltage and at 3.6 V supply voltage.