A Dynamically High-Impedance Charge-Pump-Based LDO With Digital-LDO-Like Properties Achieving a Sub-4-fs FoM

This article presents an event-driven charge-pump-based low-dropout (LDO) regulator with an ac-coupled high-impedance (ACHZ) feedback loop. By using the ACHZ loop and continuous-time dead-zone detection, the proposed LDO responds in less than a clock cycle during load transients, achieving the response and settling times of 6.9 and 65 ns, respectively, all at a 4.9-μA quiescent current for a sub-4-fs FoM. The output ripple is measured to have a stable amplitude and is <; 15 mV over the LDO's 105000× stable load range (1 μA-105 mA). In addition to all these features, the proposed LDO also retains the advantages of normal digital LDOs: process portability and the ability to operate at a low supply voltage.