Design of Capacitor-less LDO applied to Low Power Supply with High-precision Bandgap

Abstract

This paper proposes a capacitor-less low dropout regulator (LDO) applied to low power supply to meet the needs of low power consumption and highly integration. In order to improve the transient response of the system, a dynamic bias circuit is designed, which can automatically track the change of load current. In addition, the temperature coefficient of bandgap reference in conventional LDO is generally 20-100 ppm/°C. The bandgap reference circuit proposed in this paper can achieve 1.73 ppm/°C without trimming, and the accuracy is better than 1% at all process corner. The design and simulation are based on TSMC 0.18 μm CMOS process, the simulation results show that the LDO output voltage is 1 V when input power supply voltage is 1.2 V. The proposed regulator can operate with a minimum dropout voltage of 200 mV when load current is 50 mA. The maximum undershoot and overshoot voltages are 34 mV and 28 mV, respectively, with 1mA-50mA and 50mA-1mA step load current.