Design a 3A low dropout voltage regulator

Abstract

KTL1530 is a 3A Low Dropout Adjustable Voltage Regulator with overload, thermal and SOA (Safe Operating Area) protection features. It requires only two external resistors to set the output voltage, which can be down to 1.25 volts with very tight voltage regulation and line regulation. Using combination of power-NPN-transistor and PNP transistor structure in output stage brings excellent low dropout feature (1.1V) and current amplifying capability. Nowadays the low dropout voltage has become one of more and more desirable features. In addition, by introducing additional output stage power supply it achieves even lower dropout voltage for output stage, which is around 400mv at 3A full load current. This significantly reduces the power dissipation of the chip. This device is suitable for Pentium application requiring 2.8V or 2.5V from 3.3V ATX power supplies, where a low current input voltage 1V grater than the output voltage is also needed. It also can be used in some low voltage microprocessor applications, which require a lower dropout to regulate from 3.3v and 5V supplies, or be used as a post regulator for switching supplies applications. In this presentation, I will introduce the specification and schematic design of the KTL1530 and corresponding simulation results.