Design and implementation of an NMOS-based low dropout regulator with integrated charge pump for SOC applications

Liew, Jin Wei (2026) Design and implementation of an NMOS-based low dropout regulator with integrated charge pump for SOC applications. Final Year Project, UTAR.

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Abstract

This project presents the design and implementation methodology of a low-dropout regulator (LDO) employing an NMOS pass transistor, targeted for low-voltage and low-power system-on-chip (SoC) applications. Conventional PMOS-based LDOs suffer from large area requirements and limited transient response. While NMOSbased regulators are more area-efficient, they require a boosted gate drive at low supply voltages. To address this challenge, a charge pump was integrated into the design to provide sufficient gate overdrive. A cross-coupled charge pump and a foldedcascode operational amplifier (op-amp) were developed and compared in terms of boosting efficiency, load capability, and noise injection. The LDO utilizes the designed folded-cascode error amplifier, which can provide high gain under typical process corners. The regulator was specified to deliver a maximum load current of 5 mA with a stable output voltage of 1.2 V, while maintaining a power supply rejection ratio (PSRR) of at least –20 dB across the operating range. Comprehensive simulations were carried out in Silterra 130 nm CMOS technology using thick-oxide devices, with process and temperature corners spanning from –40 °C to 125 °C. The design methodology demonstrates how combining NMOS pass devices with efficient charge pump boosting and low-power Operational Transconductance Amplifier (OTA) architectures can achieve robust regulation, low quiescent current, and a wide operating voltage range, making the proposed LDO suitable for modern SoC and IoT applications.

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