LT1528 3A Low Dropout Regulator for Microprocessor Applications FEATURES DESCRIPTION n Dropout Voltage: 0.6V at I = 3A The LT 1528 is a 3A low dropout regulator optimized to OUT n Fast Transient Response handle the large load current transients associated with n Output Current: 3A the current generation of microprocessors. This device has n Quiescent Current: 400A the fastest transient response of currently available PNP n No Protection Diodes Needed regulators and is very tolerant of variations in capacitor n Fixed Output Voltage: 3.3V ESR. Dropout voltage is 75mV at 10mA, rising to 300mV n Controlled Quiescent Current in Dropout at 1A and 600mV at 3A. The device has a quiescent cur- n Shutdown I = 125A rent of 400A. Quiescent current is well controlled it does Q n Stable with 3.3F Output Capacitor not increase signi cantly as the device enters dropout. n Reverse Battery Protection The regulator can operate with output capacitors as small n No Reverse Output Current as 3.3F, although larger capacitors will be needed to n Thermal Limiting achieve the performance required in most microprocessor applications. The LT1528 is available with a xed output voltage of 3.3V. An external SENSE pin allows adjustment to output voltages greater than 3.3V, using a simple resis- APPLICATIONS tive divider. This allows the device to be adjusted over a n Microprocessor Applications wide range of output voltages, including the 3.3V to 4.2V n Post Regulator for Switching Supplies range required by a variety of processors from Intel, IBM, n 5V to 3.3V Logic Regulator AMD, and Cyrix. The LT1528 has both reverse input and reverse output protection and includes a shutdown feature. Quiescent current drops to 125A in shutdown. The LT1528 is avail- able in 5-lead TO-220 and 5-lead DD-PAK packages. L, LT, LTC and LTM are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. TYPICAL APPLICATION Microprocessor Supply with Shutdown Dropout Voltage 0.6 5 1 V IN OUT OUT 0.5 + 4 47F* 15 68 V =5V LT1528 SOLID TANTALUM IN J1 J2 J3 0.4 4 2 SHDN SENSE GND 0.3 330 3 0.2 V (PIN 4) OUTPUT SHORTING V *CHOOSE CAPACITORS SHDN OUT 0.1 TO MEET PROCESSOR <0.25 OFF J1 3.30 REQUIREMENTS >2.80 ON J2 3.45 0 NC ON J3 4.00 1528 TA01 0 0.5 1.0 1.5 2.0 2.5 3.0 OUTPUT CURRENT (mA) 1528 TA02 1528fb 1 DROPOUT VOLTAGE (V)LT1528 ABSOLUTE MAXIMUM RATINGS (Note 1) Input Voltage ........................................................ 15V* Output Short-Circuit Duration .......................... Inde nite OUTPUT Pin Reverse Current ................................10mA Storage Temperature Range ................... 65C to 150C SENSE Pin Current .................................................10mA Operating Junction Temperature Range SHDN Pin Input Voltage (Note 2) ..................6.5V, 0.3V LT1528C ................................................ 0C to 125C SHDN Pin Input Current (Note 2) .............................5mA Lead Temperature (Soldering, 10 sec) .................. 300C *For applications requiring input voltage ratings greater than 15V, contact the factory. PIN CONFIGURATION TAB IS FRONT VIEW FRONT VIEW GND 5 V IN 5 V IN 4 SHDN 4 SHDN TAB IS 3 GND 3 GND GND 2 SENSE 2 SENSE 1 OUTPUT 1 OUTPUT Q PACKAGE T PACKAGE 5-LEAD PLASTIC DD 5-LEAD PLASTIC TO-220 T = 125C, = 30C/ W T = 125C, = 50C/ W JMAX JA JMAX JA ORDER INFORMATION LEAD FREE FINISH TAPE AND REEL PART MARKING PACKAGE DESCRIPTION TEMPERATURE RANGE LT1528CQ PBF LT1528CQ TRPBF LT1528CQ 5-Lead Plastic DD-PAK 0C to 125C LT1528CT PBF LT1528CT TRPBF LT1528CT 5-Lead Plastic TO-220 0C to 125C LEAD BASED FINISH TAPE AND REEL PART MARKING PACKAGE DESCRIPTION TEMPERATURE RANGE LT1528CQ LT1528CQ TR LT1528CQ 5-Lead Plastic DD-PAK 0C to 125C LT1528CT LT1528CT TR LT1528CT 5-Lead Plastic TO-220 0C to 125C Consult LTC Marketing for parts speci ed with wider operating temperature ranges. For more information on lead free part marking, go to: