A Design of a 92.4% Efficiency Triple Mode Control DC–DC Buck Converter With Low Power Retention Mode and Adaptive Zero Current Detector for IoT/Wearable Applications

This paper presents a retention/ pulse frequency modulation (PFM)/ pulse width modulation (PWM) mode dc–dc buck converter with adaptive zero current detector (AZCD) and spread spectrum clock generation (SSCG) for IoT/Wearable systems. The proposed dc–dc buck converter is capable of handling loads from 10 μA to 20 mA with high efficiency by applying triple mode (retention mode, PFM mode, and PWM mode), gate split technique, and AZCD. Retention mode is proposed to extend wide load range at ultralight load. Gate split technique adjusts the conduction loss and switching loss. AZCD reduces the operation duty of the high-speed comparator and avoid reverse current below light load. In IoT applications, each node communicates with other nodes through a Bluetooth low energy transceiver, which consumes very low current and is highly sensitive to supply noise. Therefore, the proposed dc–dc buck converter adopts the SSCG technique to reduce electromagnetic interference by up to 18 dB. This chip is implemented using 0.13 μm CMOS technology with an active area of
$\text{820}\times \text{800}\;\mu \text{m}^{2}$
. The maximum power efficiency of the proposed dc–dc buck converter is 92.4% at a switching frequency of 2.5 MHz when the load current range is 10 to 20 mA. The input voltage range and the regulated output voltage are 2.2–3.3 and 1.7 V, respectively. In addition, the proposed dc–dc buck converter achieves over 74.2% efficiency in retention mode when the load current range is from 10 to 500 μA.