LT1371 500kHz High Efficiency 3A Switching Regulator DESCRIPTION FEATURES n Faster Switching with Increased Efficiency The LT 1371 is a monolithic high frequency current mode n Uses Small Inductors: 4.7H switching regulator. It can be operated in all standard n All Surface Mount Components switching configurations including boost, buck, flyback, n Low Minimum Supply Voltage: 2.7V forward, inverting and Cuk. A 3A high efficiency switch n Quiescent Current: 4mA Typ is included on the die, along with all oscillator, control and n Current Limited Power Switch: 3A protection circuitry. n Regulates Positive or Negative Outputs The LT1371 typically consumes only 4mA quiescent n Shutdown Supply Current: 12A Typ current and has higher efficiency than previous parts. n Easy External Synchronization High frequency switching allows for very small inductors to be used. U APPLICATIONS New design techniques increase flexibility and maintain ease of use. Switching is easily synchronized to an exter- n Boost Regulators nal logic level source. A logic low on the Shutdown pin n Laptop Computer Supplies reduces supply current to 12A. Unique error amplifier n Multiple Output Flyback Supplies circuitry can regulate positive or negative output voltage n Inverting Supplies while maintaining simple frequency compensation tech- niques. Nonlinear error amplifier transconductance re- duces output overshoot on start-up or overload recovery. Oscillator frequency shifting protects external compo- nents during overload conditions. , LTC and LT are registered trademarks of Linear Technology Corporation. TYPICAL APPLICATION 5V to 12V Boost Converter 12V Output Efficiency D1 5V 100 L1* V = 5V MBRS330T3 IN 4.7H V OUT 12V 90 V R1 IN 53.6k ON V S/S SW OFF 1% 80 LT1371 C4** * COILCRAFT DO3316P-472 (4.7H), + + C1** FB 22F DO3316P-103 (10H) OR 22F 70 25V GND V SUMIDA CD104-100MC (10 H) 25V C 2 ** R2 AVX TPSD226M025R0200 6.19k 60 MAX I OUT C2 1% 0.047F L1 I OUT R3 C3 4.7H 0.7A 2k 0.0047F 50 10H 0.8A 0.01 0.1 1 LT1371 TA01 OUTPUT CURRENT (A) LT1371 TA02 1 EFFICIENCY (%) U ULT1371 ABSOLUTEXAI U RATI GS Supply Voltage ....................................................... 30V Operating Ambient Temperature Range ...... 0C to 70C Switch Voltage Operating Junction Temperature Range LT1371 ............................................................... 35V Commercial .......................................... 0C to 125C LT1371HV .......................................................... 42V Industrial ......................................... 40C to 125C S/S, SHDN, SYNC Pin Voltage ................................ 30V Short Circuit ......................................... 0C to 150C Feedback Pin Voltage (Transient, 10ms) .............. 10V Storage Temperature Range ................ 65C to 150C Feedback Pin Current........................................... 10mA Lead Temperature (Soldering, 10 sec)................. 300C Negative Feedback Pin Voltage (Transient, 10ms) ............................................. 10V PACKAGE/ORDER I FOR ATIO FRONT VIEW ORDER PART ORDER PART 7 V IN NUMBER NUMBER 6 S/S TAB 5 V SW TOP VIEW IS 4 GND LT1371CSW LT1371CR GND 3 NFB V 1 20 V C SW 2 FB LT1371HVCR LT1371HVCSW FB 2 19 NC 1 V C LT1371ISW LT1371IR NFB 3 18 V SW R PACKAGE LT1371HVIR LT1371HVISW 7-LEAD PLASTIC DD GND 4 17 GND T = 125C, = 30C/W JMAX JA GND 5 16 GND 2 WITH PACKAGE SOLDERED TO 0.5 INCH COPPER GND 6 15 GND AREA OVER BACKSIDE GROUND PLANE OR INTERNAL POWER PLANE. CAN VARY FROM 20C/W TO GND 7 14 GND JA >40C/W DEPENDING ON MOUNTING TECHNIQUE SHDN 8 13 NC SYNC 9 12 NC ORDER PART FRONT VIEW V 10 11 GND IN NUMBER 7 V IN 6 SW PACKAGE S/S TAB 5 20-LEAD PLASTIC SO WIDE V SW LT1371CT7 IS 4 GND T = 125C, = 50C/W JMAX JA GND 3 NFB LT1371HVCT7 2 FB WILL VARY FROM APPROXIMATELY 40C/W WITH JA 1 LT1371IT7 V 2 2 C 0.75 INCH OF 1 OZ COPPER TO 50C/W WITH 0.33 INCH OF 1 OZ COPPER ON A DOUBLE-SIDED BOARD LT1371HVIT7 T7 PACKAGE 7-LEAD TO-220 T = 125C, = 50C/W, = 4C/W JMAX JA JC Consult factory for Military grade parts. ELECTRICAL CHARACTERISTICS V = 5V, V = 0.6V, V = V , V , S/S, SHDN, SYNC and NFB pins open, unless otherwise noted. IN C FB REF SW SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS V Reference Voltage Measured at Feedback Pin 1.230 1.245 1.260 V REF V = 0.8V l 1.225 1.245 1.265 V C I Feedback Input Current V = V 250 550 nA FB FB REF l 900 nA Reference Voltage Line Regulation 2.7V V 25V, V = 0.8V l 0.01 0.03 %/V IN C 2 U WU U W W W