A 470-nA Quiescent Current and 92.7%/94.7% Efficiency DCT/PWM Control Buck Converter With Seamless Mode Selection for IoT Application

An ultra-low quiescent current dual-mode buck converter system is designed for IoT application, which includes a double clock time (DCT) and a pulse-width-modulation (PWM) control modes. The proposed DCT mode can reduce the conversion loss over a wide loading range from nA-to-mA and achieve seamless mode transition from DCT to PWM control. Implemented in a <inline-formula> <tex-math notation="LaTeX">$0.18\mu \text{m}$ </tex-math></inline-formula> CMOS, this converter achieves a peak efficiency of 92.7%/94.7% in DCT/PWM and >80% efficiency from <inline-formula> <tex-math notation="LaTeX">$10~\mu $ </tex-math></inline-formula> A to 50 mA (5000x), with a wide input voltage from 2 V to 5 V. A quiescent current of 470 nA including bandgap voltage reference and internal oscillator is achieved. The DCT-to-PWM mode selection mechanism achieves an undershoot of 80 mV at <inline-formula> <tex-math notation="LaTeX">$11~\mu \text{s}$ </tex-math></inline-formula> recovery time when load current jumps from <inline-formula> <tex-math notation="LaTeX">$6.67~\mu \text{A}$ </tex-math></inline-formula> to 50 mA.