A 1.14-fs FOM off-chip capless LDO with fast transient response for low-power IoT devices

Abstract

This brief presents a 0.18-μm BCD low-dropout regulator (LDO) designed for low-power Internet of Things (IoT) devices that achieves fast transient responses with a nA-level quiescent current (IQ) and operates without external capacitors. The power supply voltage can be reduced to 0.9 V, consuming only 284 nA of quiescent current. The design incorporates an adaptive bias and a class-AB OTA with dual Gm stages, achieving low IQ. Its second stage forms a feedforward path, utilizing only a 2 pF compensation capacitor. The combination of this feedforward path and an FVF buffer with body bias modulation enables zero-point load tracking compensation technology, ensuring loop stability under light loads in this capacitor-less LDO. Moreover, reducing the size of the pass transistor MP minimizes the overall area of the LDO to just 0.005 mm². An FVF buffer integrated with a comparator-based transient enhancement circuit improves the LDO’s transient response. Post-simulation results demonstrate a load regulation of 0.0974 mV/mA, and a superior transient figure-of-merit (FOM) of 1.14-fs.