A 14.8μ VRMS Integrated Noise Output Capacitor-less Low Dropout Regulator with a Switched-RC Bandgap Reference

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 95.3 mu V-RMS to 14.8 mu V-RMS. The LDO delivers a maximum load current of 100mA with a dropout voltage of 230mV and quiescent current consumption of 40 mu A. It achieves a PSR of 50dB at 10kHz for programmable output voltage range of 1V-3.3V. Fabricated in a 0.25 mu m CMOS process, the LDO core occupies an area of 0.18mm(2).