A 430-mA Capacitor Less Analog Assisted Hybrid LDO With Fast Transient Algorithm

This paper presents an analog-assisted hybrid low-dropout regulator (LDO) with a wide load current range and fast transient response. The proposed design is composed of digital and analog loops of which the transient response is dictated by the digital portion. A fast approximation algorithm leveraging charge distribution reduces settling time significantly compared to linear and SAR approaches. A wide load range droop detector further improves transient response with negligible power overhead. The analog assisted circuits continuously provide current in response to the load current change without disturbing the loop dynamic. Implemented in a TSMC 180-nm standard CMOS technology, the LDO supports a 430 mA maximum load and ensures loop stability without external capacitors. It achieves a 480 mV undershoot at 430 mA with 100 ns edge time, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$49~\mu $ </tex-math></inline-formula>A quiescent current, and settling times of 225 ns and 260 ns for undershoot and overshoot at <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$C_{L}=0$ </tex-math></inline-formula> pF when a 10-MHz clock is used. Measurement shows that activating the droop detector reduces undershoot by 54%.