A robust frequency compensation scheme for LDO voltage regulators

Abstract—A stable low dropout (LDO) voltage regulator topology for low equivalent series resistance (ESR) capacitive loads is presented. The proposed scheme generates a zero inter-nally instead of relying on the zero generated by the load capacitor and its ESR combination for stability. It is demonstrated that this scheme realizes robust frequency compensation, facilitates the use of multilayer ceramic capacitors for the load of LDO regulators, and improves transient response and noise performance. Test results from a prototype fabricated in AMI 0.5- m CMOS tech-nology provide the most important parameters of the regulator viz., ground current, load regulation, line regulation, output noise, and start-up time. Index Terms—Frequency compensation, linear regulators, low dropout (LDO) regulator, LDO stability, power management. I