A 14.8μVRMS integrated noise output capacitor-less low dropout regulator with a switched-RC bandgap reference

Abstract

Achieving low noise is becoming an important requirement in linear supply regulators for RF and mixed-signal SoC applications. A low-noise, low dropout regulator using switched-RC bandgap reference and a multi-loop, unconditionally stable error amplifier for output capacitor-less operation is presented. Switched-RC sample-and-hold filtered bandgap reference and current-mode chopped error amplifier techniques are used for reducing output noise of the LDO. A switched capacitor notch filter is used to ensure chopping ripple free output voltage. The proposed techniques reduce the 10Hz to 100kHz integrated output noise of the LDO from 95.3uVrms to 14.8μVrms. The LDO delivers a maximum load current of 100mA with a dropout voltage of 230mV and quiescent current consumption of 40μA. It achieves a PSR of 50dB at 10kHz for programmable output voltage range of 1V-3.3V. Fabricated in a 0.25μm CMOS process, the LDO core occupies an area of 0.18mm2.