LT1270A/LT1270 8A and 10A High Efficiency Switching Regulators FEATURES DESCRIPTIO n The LT1270A/LT1270 are monolithic high power switch- Wide Input Voltage Range: 3.5V to 30V n Low Quiescent Current: 7mA ing regulators. Identical to the popular LT1070, except for n switching frequency (60kHz) and higher switch current, Internal 8A Switch (10A for LT1270A) n they can be operated in all standard switching configura- Very Few External Parts Required n Self-Protected Against Overloads tions including buck, boost, flyback, and inverting. A high n current, high efficiency switch is included on the die along Shutdown Mode Draws Only 100A Supply Current n with all oscillator, control, and protection circuitry. Inte- Flyback-Regulated Mode Has Fully Floating Outputs n Can be Externally Synchronized gration of all functions allows the LT1270A/LT1270 to be built in a standard TO-220 power package. This makes it (See LT1072 Data Sheet) n extremely easy to use and provides bust proof operation Comes in Standard 5-Pin TO-220 Package U similar to that obtained with 3-pin linear regulators. APPLICATIO S The LT1270A/LT1270 operate with supply voltages from n High Efficiency Buck Converter 3.5V to 30V, and draw only 7mA quiescent current. By n PC Power Supply with Multiple Outputs utilizing current-mode switching techniques, they provide n Battery Upconverter excellent AC and DC load and line regulation. n Negative-to-Positive Converter The LT1270A/LT1270 use adaptive anti-sat switch drive to USER NOTE: allow very wide ranging load currents with no loss in This data sheet is only intended to provide specifications, graphs and a general functional efficiency. An externally activated shutdown mode re- description of the LT1270A/LT1270. Application circuits are included to show the capability of the LT1270A/LT1270. A complete design manual (AN-19) should be obtained to assist in developing duces total supply current to 100A typical for standby new designs. AN-19 contains a comprehensive discussion of both the LT1070 and the external components used with it, as well as complete formulas for calculating the values of these operation. components. AN-19 can also be used for the LT1270A/LT1270 by factoring in the higher switch current rating and higher operating frequency. A comprehensive CAD program called SwitcherCad is also available. Contact the local sales office in your area or the factory direct. TYPICAL APPLICATIO Maximum Output Power* High Efficiency Buck Converter 100 BOOST EFFICIENCY IS 88% 2A, 86% 5A. V IN V FOR m POWER SHUTDOWN OPTION, CONSULT FACTORY. BUCK-BOOST, 80 SW (8V TO 25V) V = 12V *THESE COMPONENTS RATED CONSERVATIVELY TO O 1N5819 LT1270* (INVERTING) IMPROVE EFFICIENCY. MAXIMUM OUTPUT CURRENT V FB IN CAN BE 7A. FOR HIGH EFFICIENCY, THE INDUCTOR SHOULD 60 GND V C BE MOLYPERMALLOY OR FERRITE. FLYBACK 1m F 0.047m F 0.047m F 40 1k 35m H, 8A* 5V* BUCK-BOOST, V = 5V 5A 20 O (INVERTING) 9.1k ANODE LT1431CZ REF 470m F 0 MBR1035* 35V CATHODE 0 5 10 15 20 25 30 10k INPUT VOLTAGE (V) 2N3904 LT1270 TA02 1N4158 1000m F *MULTIPLY BY 1.2 FOR LT1270A. 360W 560W 25V BUCK MODE OUTPUT POWER (7.5A)(V ) OUT LT1270 TA01 TRANSFORMER TURNS RATIO MUST BE OPTIMUM TO ACHIEVE FULL POWER 1270afc 1 OUTPUT POWER (W) + + U ULT1270A/LT1270 ABOLUEXAIURATGS PACKAGE/ORDER I FOR ATIO S T I (Note 1) Supply Voltage ....................................................... 30V ORDER PART FRONT VIEW Switch Output Voltage ............................................ 60V NUMBER 5 V IN Feedback Pin Voltage (Transient, 1ms) ................ 15V 4 V SW TAB IS 3 GND Operating Junction Temperature Range LT1270CT GND 2 FB LT1270AC/LT1270C (Oper.)................ 0C to 125C LT1270ACT 1 V C LT1270AC/LT1270C (Short-Ckt) ......... 0C to 140C T PACKAGE 5-LEAD PLASTIC TO-220 Storage Temperature Range ................ 65c to 150C T = 100C, = 2C/W, = 50C/W JMAX JA JA Lead Temperature (Soldering, 10 sec)................ 300C Consult LTC Marketing for parts specified with wider operating temperature ranges. ELECTRICAL CHARACTERISTICS The l denotes specifications which apply over the full operating tempera- ture range, otherwise specifications are at T = 25C. V = 15V, V = 0.5V, V = V , switch pin open, unless otherwise noted. A 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 1100 nA gm Error Amplifier l = 25A 3000 4400 6000 mho C Transconductance l 2400 7000 mho Error Amplifier Source of V = 1.5V 150 200 350 A C Sink Current l 120 400 A Error Amplifier Clamp Voltage Hi Clamp, V = 1V 1.80 2.30 V FB Lo Clamp, V = 1.5V 0.25 0.38 0.52 V FB Reference Voltage Line Regulation 3V V V , V = 0.8V l 0.03 %/V IN MAX C A Error Amplifier Voltage Gain 0.9V V 1.4V 500 800 V/V V C Minimum Input Voltage l 2.8 3.0 V I Supply Current 3V V V , V = 0.6V 7 10 mA Q IN MAX C Control Pin Threshold Duty Cycle = 0 0.70 0.90 1.08 V l 0.50 1.25 V Normal/Flyback Threshold 0.40 0.45 0.54 V on Feedback Pin V Flyback Reference Voltage I = 50A 15.0 16.3 17.6 V FB FB l 14.0 18.0 V V Change in Flyback Reference 0.05 I 1mA 4.5 6.8 8.5 V FB FB Voltage Flyback Reference Voltage I = 50A 0.01 0.03 %/V FB Line Regulation 3V V V IN MAX Flyback Amplifier l = 10A 150 300 650 mho C Transconductance (gm) Flyback Amplifier Source V = 0.6V Source l 15 32 70 A C = 50A Sink l 25 40 70 A and Sink Current I FB BV Output Switch Breakdown 3V V V l 60 75 V IN MAX Voltage I = 1.5mA SW V Output Switch ON T 100C 0.12 0.18 SAT J Resistance (Note 2, 4) T 125C 0.22 J Control Voltage to Switch 12 A/V Current Transconductance Switch Current Limit (LT1270) Duty Cycle = 50%, T 100C l816 A LIM J (Note 4) Duty Cycle = 80%, T 100C l614 A J 1270afc 2 U WU UWWW