Compensation Scheme for High Bandwidth LDOs with Large Parasitic ESL

This paper presents a compensation scheme for an externally compensated low drop-out (LDO) regulator, which has to provide fast high-load currents with low-noise and high-PSRR. The approach overcomes the challenge of the presence of large parasitics (ESR and ESL) when the external capacitor is placed far away from the chip, which is becoming more common in many space constrained electronic modules. The proposed scheme has been validated in a 5V LDO designed in TSMC's 40nm DMOS technology. It delivers 200ns wide 200mA current pulses while maintaining low noise and high PSRR (40dB) up to 1MHz. The LDO is stabilized with an external 2.2 μF capacitor and can accommodate large bonding parasitics (up to 4nH).