LT1521/LT1521-3 LT1521-3.3/LT1521-5 300mA Low Dropout Regulators with Micropower Quiescent Current and Shutdown UFEATURESDESCRIPTIO ■ Dropout Voltage: 0.5V The LT®1521/LT1521-3/LT1521-3.3/LT1521-5 are low ■ Output Current: 300mA dropout regulators with micropower quiescent current ■ Quiescent Current: 12 µ A and shutdown. These devices are capable of supplying ■ No Protection Diodes Needed 300mA of output current with a dropout voltage of 0.5V. ■ Adjustable Output from 3.8V to 20V Designed for use in battery-powered systems, the low ■ Fixed Output Voltages: 3V, 3.3V, 5V quiescent current, 12µA operating and 6µA in ■ Controlled Quiescent Current in Dropout shutdown, makes them an ideal choice. The quiescent ■ Shutdown I current is well controlled; it does not rise in dropout as it Q = 6µA ■ Reverse Battery Protection does with many other low dropout PNP regulators. ■ No Reverse Current Other features of the LT1521/LT1521-3/LT1521-3.3/ ■ Thermal Limiting LT1521-5 include the ability to operate with very small U output capacitors. They are stable with only 1.5µF on the APPLICATIO S output while most older devices require between 10µF and ■ 100µF for stability. Small ceramic capacitors can be used, Low Current Regulator ■ enhancing manufacturability. Also, the input may be con- Regulator for Battery-Powered Systems ■ nected to voltages lower than the output voltage, including Post Regulator for Switching Supplies negative voltages, without reverse current flow from out- put to input. This makes the LT1521 series ideal for backup power situations where the output is held high and the input is low or reversed. Under these conditions only 5µA will flow from the output pin to ground. , LTC and LT are registered trademarks of Linear Technology Corporation. UTYPICAL APPLICATIO5V Battery-Powered Supply with ShutdownDropout Voltage 0.6 8 1 5V IN OUT 300mA + 0.5 6V 1µF LT1521-5 1.5µF 0.4 5 2 SHDN SENSE GND 0.3 3 0.2 DROPOUT VOLTAGE (V) VSHDN (PIN 5) OUTPUT <0.25 OFF 0.1 >2.80 ON LT1521 • TA01 NC ON 0 0 50 100 150 200 250 300 OUTPUT CURRENT (mA) LT1521 • TA02 1521335fb 1