A fully integrated ultra-low noise low-dropout regulator inherently combined with bandgap reference for SoC applications

This paper presents a capacitor-less ultra-low noise low-dropout regulator (LDO) inherently combined with bandgap reference (BGR). Compared to traditional LDOs with a dedicated error amplifier (EA) followed by a BGR to generate a variety of desired output voltages through power transistors, the proposed LDO uses a novel architecture, which employs a BGR inherently combined with LDO sharing the same operational amplifier (OPA) for the voltage generation. By doing so this architecture not only reduces LDO's power consumption and design complexity, but also greatly improves its low-frequency noise characteristic due to much less noise contribution from the active part of EA. The design procedure of the proposed LDO is presented with its implementation in the 40 nm CMOS process. The post-simulation results show that the output voltage ranges from 1.27 V to 2.67 V at a power supply of 3.3 V, with an average temperature coefficient (TC) of 11.9 ppm/°C over a temperature range (TR) of −40 °C to 125 °C. With an LDO output voltage of 1.27 V and a load current of 10 mA, the output noise is as low as 2.61 μV/Hz at 1 Hz and the integrated noise is 5.09 μVRMS from 1 Hz to 100 Hz. The quiescent current is only 30 μA in standby mode. The proposed LDO occupies an area of 0.036 mm2. This ultra-low noise LDO is quite suitable for low-frequency signal conditioning circuit and system design, such as Doppler radar transceivers and bio-medical circuit and system.