The LT1528 is a 3A low dropout regulator optimized to handle the large load current transients associated with the current generation of microprocessors. This device has the fastest transient response of currently available PNP regulators and is very tolerant of variations incapacitor ESR. Dropout voltage is 75mV at 10mA, rising to 300mV at 1A and 600mV at 3A. The device has a quiescent current of 400µA. Quiescent current is well controlled; it does not increase significantly as the device enters dropout. The regulator can operate with output capacitors as small as 3.3µF, although larger capacitors will be needed to achieve the performance required in most microprocessor applications. The LT1528 is available with a fixed output voltage of 3.3V. An external SENSE pin allows adjustment to output voltages greater than 3.3V, using a simple resistive divider. This allows the device to be adjusted over a wide range of output voltages, including the 3.3V to 4.2V range required by a variety of processors from Intel, IBM, AMD, and Cyrix.The LT1528 has both reverse input and reverse output protection and includes a shutdown feature. Quiescent current drops to 125µA in shutdown. The LT1528 is available in 5-lead TO-220 and 5-lead DD-PAK packages.ApplicationsMicroprocessor ApplicationsPost Regulator for Switching Supplies5V to 3.3V Logic Regulator