LT1271/LT1269 4A High Efficiency Switching Regulators DESCRIPTIO FEATURES n Wide Input Voltage Range 3.5V to 30V The LT 1271 and LT1269 are monolithic high power n Low Quiescent Current: 7mA switching regulators. Identical to the popular LT1070, n Internal 4A Switch except for switching frequency (LT1271 = 60kHz, LT1269 n Very Few External Parts Required = 100kHz) and slightly lower switch current, they can be n Self Protected Against Overloads operated in all standard switching configurations includ- n Shutdown Mode Draws Only 100A Supply Current ing buck, boost, flyback and inverting. A high current, high n Flyback Regulated Mode Has Fully Floating Outputs efficiency switch is included on the die along with all n Comes in Standard 5-Pin Package oscillator, control and protection circuitry. Integration of n Can Be Externally Synchronized (See LT1072 Data Sheet) all functions allows the LT1271/LT1269 to be built in a standard TO-220 power package. This makes them ex- APPLICATI S tremely easy to use and provides bust proof operation n similar to that obtained with 3-pin linear regulators. Boost Converter n High Efficiency Buck Converter The LT1271/LT1269 operate with supply voltages from n PC Power Supply with Multiple Outputs 3.5V to 30V, and draw only 7mA quiescent current. By n Battery Up-Converter utilizing current mode switching techniques, they pro- n Negative-to-Positive Converter vides excellent AC and DC load and line regulation. USER NOTE: A patented adaptive antisat switch drive allows very wide This data sheet is only intended to provide specifications, graphs, and a general functional description of the LT1271/LT1269. Application circuits are included to show the capability of the ranging load currents with no loss in efficiency. An exter- LT1271/LT1269. A complete design manual (AN-19) should be obtained to assist in developing new designs. This manual contains a comprehensive discussion of both the LT1070 and the external nally activated shutdown mode reduces total supply cur- components used with it, as well as complete formulas for calculating the values of these components. The manual can also be used for the LT1271/LT1269 by factoring in the higher switch rent to 100A typical for standby operation. current rating and higher operating frequency. , LTC and LT are registered trademarks of Linear Technology Corporation. Burst Mode is a trademark of Linear Technology Corporation. TYPICAL APPLICATION TM High Efficiency 5V Regulator with Burst Mode Operation Maximum Output Power 50 V IN V V SW IN 6.5V TO 25V BOOST BUCK-BOOST 40 V = 12V O LT1271 EFFICIENCY 90% (INVERTING) AT I = 0.4A TO 1.5A OUT FB 30 V GND C FLYBACK 1N4148 0.02F 20 L1 + 680 0.03F 4.7F 25H TANT TO 50H 0.1F BUCK-BOOST 0.015 10 V OUT V = 5V O 5V, 3A (INVERTING) MBR + 330pF 390F 0 16V 0 5 10 15 20 25 30 INPUT VOLTAGE (V) + V DIODE V C 1271/69 TA02 V V LIM BUCK MODE OUTPUT POWER (3.5A)(V ) IN OUT + C1 LT1432 TRANSFORMER TURNS RATIO MUST BE 200F V OUT OPTIMUM TO ACHIEVE FULL POWER. 35V MODE GND <0.3V = NORMAL RUN MODE >2.5V = SHUTDOWN OPEN = BURST MODE OPERATION 127/691 TA01 1 OUTPUT POWER (W) U UO ULT1271/LT1269 ABSOLUTEXAI U RATI GS Supply Voltage ....................................................... 30V Operating Junction Temperature Range Switch Output Voltage ............................................ 60V Operating.............................................. 0C to 100C Feedback Pin Voltage (Transient, 1ms) ................ 15V Short Circuit ......................................... 0C to 125C Storage Temperature Range ................ 65C to 150C Lead Temperature (Soldering, 10 sec.)................ 300C PACKAGE/ORDER I FOR ATIO FRONT VIEW ORDER PART ORDER PART 5 V IN NUMBER TOP VIEW NUMBER 4 V SW V 1 20 V SW SW 3 GND LT1271CQ V 2 19 V LT1269CS SW SW 2 FB NC 3 18 NC LT1269CQ 1 V C GND 4 17 GND Q PACKAGE GND 5 16 GND POWER POWER 5-LEAD PLASTIC DD SWITCH SWITCH GND 6 15 GND T = 100C, = 4C/W, = 30C/W* J MAX JC JA GND 7 14 GND FRONT VIEW AGND 8 13 V IN ORDER PART V 9 5 V 12 NC C IN NUMBER 4 V FB 10 11 NC SW 3 GND SW PACKAGE LT1271CT 2 20-LEAD PLASTIC WIDE SO FB LT1269CT 1 V WILL VARY FROM APPROXIMATELY 40C/W C WITH 0.75 SQ. IN. OF 1 OZ. COPPER TO 46C/W T PACKAGE WITH 0.33 SQ. IN. OF 1 OZ. COPPER 5-LEAD PLASTIC TO-220 T = 100C, = 4C/W, = 50C/W J MAX JC JA *With device soldered to 1/2 square inch of 1oz copper over backside or internal layer ground plane. Consult factory for Industrial and Military grade parts. ELECTRICAL CHARACTERISTICS V = 15V, V = 0.5V, V = V switch pin open, unless otherwise noted. IN C FB REF, SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS V Reference Voltage Measured at Feedback Pin 1.224 1.244 1.264 V REF V = 0.8V l 1.214 1.244 1.274 V C I Feedback Input Current V = V 350 750 nA B FB REF l 1100 nA gm Error Amplifier I = 25A 3000 4400 6000 mho C Transconductance l 2400 7000 mho Error Amplifier Source or V = 1.5V 150 200 350 A C Sink Current l 120 400 A Error Amplifier Clamp Hi Clamp, V = 1V 1.8 2.3 V FB Voltage Lo Clamp, V = 1.5V 0.25 0.38 0.52 V FB Reference Voltage Line 3V V V V = 0.8V l 0.03 %/V IN MAX, C Regulation A Error Amplifier Voltage Gain 0.9V V 1.4V 500 800 V/V V C Minimum Input Voltage (Note 3) l 2.8 3.0 V I Supply Current 3V V V , V = 0.6V 7 10 mA Q IN MAX C 2 U WU U W W W