A fast low dropout regulator for digital systems

• Main Author: Jiang, Yushan
• Other Authors: Chan Pak Kwong
• Format: Final Year Project
• Language: English
• Published: 2016
• Subjects: DRNTU::Engineering
• Online Access: http://hdl.handle.net/10356/68332
• Institution: Nanyang Technological University

Low Dropout (LDO) voltage regulator is an important building block, especially power management ICs for SOC applications, due to popular portable devices. An LDO can provide a regulated, stable voltage for subsequent circuits with various loading conditions. For a digital system, fast response with small settling time and low noise are essential to avoid system error. Precise output voltage and good power efficiency are major consideration for low power devices. The proposed LDO regulator provides a 200mV dropout voltage with 0.9V supply voltage. A Flipped Voltage Follower (FVF) based voltage regulator with output capacitor-less characteristic is used. This meets the need of reducing chip area. With an ac coupling network to detect the spike and to response in a fast loop, fast transient performance is achieved. The compensation technique is based on the combination of Miller compensation and DFC compensation. It ensures the stability of the LDO’s function. Besides, additional gain stage in feedback loop is employed to achieve high loop gain, leading to good load and line regulations. Validated by UMC 65nm CMOS process, the proposed LDO regulator achieves the load capacitance driving capability up to 3nF. It can achieve the stability with a driving load current ranging from 0mA to 10mA, whilst consuming a low quiescent current less than 20µA. Furthermore, the load transient response with <1µs setting time is achieved with minimized voltage spike. This is useful for driving on-chip low-power microcontroller system. Comparing the simulation results with that of other reported capacitor-less LDO regulators, the proposed LDO regulator has a better figure of merit (FOM) and has offered other comparable performance metrics.