LT1270ACT#PBF

LT1270A/LT1270 8A and 10A High Efficiency Switching Regulators U FEATURES ■ ■ ■ ■ ■ ■ ■ ■ ■ DESCRIPTIO The LT1270A/LT1270 are monolithic high power switching regulators. Identical to the popular LT1070, except for switching frequency (60kHz) and higher switch current, they can be operated in all standard switching configurations including buck, boost, flyback, and inverting. A high current, high efficiency switch is included on the die along with all oscillator, control, and protection circuitry. Integration of all functions allows the LT1270A/LT1270 to be built in a standard TO-220 power package. This makes it extremely easy to use and provides “bust proof” operation similar to that obtained with 3-pin linear regulators. Wide Input Voltage Range: 3.5V to 30V Low Quiescent Current: 7mA Internal 8A Switch (10A for LT1270A) Very Few External Parts Required Self-Protected Against Overloads Shutdown Mode Draws Only 100µA Supply Current Flyback-Regulated Mode Has Fully Floating Outputs Can be Externally Synchronized (See LT1072 Data Sheet) Comes in Standard 5-Pin TO-220 Package U APPLICATIO S ■ ■ ■ ■ The LT1270A/LT1270 operate with supply voltages from 3.5V to 30V, and draw only 7mA quiescent current. By utilizing current-mode switching techniques, they provide excellent AC and DC load and line regulation. High Efficiency Buck Converter PC Power Supply with Multiple Outputs Battery Upconverter Negative-to-Positive Converter The LT1270A/LT1270 use adaptive anti-sat switch drive to allow very wide ranging load currents with no loss in efficiency. An externally activated shutdown mode reduces total supply current to 100µA typical for standby operation. USER NOTE: This data sheet is only intended to provide specifications, graphs and a general functional 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 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 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. U TYPICAL APPLICATIO Maximum Output Power* High Efficiency† Buck Converter 100 EFFICIENCY IS ≈ 88% @ 2A, 86% @ 5A. FOR µPOWER SHUTDOWN OPTION, CONSULT FACTORY. *THESE COMPONENTS RATED CONSERVATIVELY TO IMPROVE EFFICIENCY. MAXIMUM OUTPUT CURRENT CAN BE 7A. FOR HIGH EFFICIENCY, THE INDUCTOR SHOULD BE MOLYPERMALLOY OR FERRITE. BOOST † VSW 1N5819 LT1270* VIN FB GND VC + 1µF 0.047µF 0.047µF 1k 35µH, 8A* 5V* 5A ANODE + 470µF 35V LT1431CZ REF CATHODE MBR1035* 1N4158 560Ω 60 FLYBACK† 40 BUCK-BOOST, VO = 5V (INVERTING) 20 9.1k 0 0 10k 2N3904 360Ω BUCK-BOOST, VO = 12V (INVERTING) 80 OUTPUT POWER (W) VIN (8V TO 25V) 5 15 20 10 INPUT VOLTAGE (V) 25 30 LT1270 • TA02 1000µF 25V LT1270 • TA01 *MULTIPLY BY 1.2 FOR LT1270A. BUCK MODE OUTPUT POWER ≈ (7.5A)(VOUT) † TRANSFORMER TURNS RATIO MUST BE OPTIMUM TO ACHIEVE FULL POWER 1270afc 1 LT1270A/LT1270 U U RATI GS W W W W AXI U U ABSOLUTE PACKAGE/ORDER I FOR ATIO (Note 1) Supply Voltage ....................................................... 30V Switch Output Voltage ............................................ 60V Feedback Pin Voltage (Transient, 1ms) ................ ±15V Operating Junction Temperature Range LT1270AC/LT1270C (Oper.) ................ 0°C to 125°C LT1270AC/LT1270C (Short-Ckt) ......... 0°C to 140°C Storage Temperature Range ................ – 65°c to 150°C Lead Temperature (Soldering, 10 sec)................ 300°C FRONT VIEW TAB IS GND 5 VIN 4 VSW 3 GND 2 FB 1 VC ORDER PART NUMBER LT1270CT LT1270ACT T PACKAGE 5-LEAD PLASTIC TO-220 TJMAX = 100°C, θJA = 2°C/W, θJA = 50°C/ W Consult LTC Marketing for parts specified with wider operating temperature ranges. ELECTRICAL CHARACTERISTICS The ● denotes specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VIN = 15V, VC = 0.5V, VFB = VREF, switch pin open, unless otherwise noted. SYMBOL VREF PARAMETER Reference Voltage IB Feedback Input Current gm Error Amplifier Transconductance Error Amplifier Source of Sink Current Error Amplifier Clamp Voltage AV IQ Reference Voltage Line Regulation Error Amplifier Voltage Gain Minimum Input Voltage Supply Current Control Pin Threshold CONDITIONS Measured at Feedback Pin VC = 0.8V VFB = VREF ● ∆lC = ±25µA ● VC = 1.5V ● Hi Clamp, VFB = 1V Lo Clamp, VFB = 1.5V 3V ≤ VIN ≤ VMAX, VC = 0.8V 0.9V ≤ VC ≤ 1.4V VFB BV VSAT LIM Change in Flyback Reference Voltage Flyback Reference Voltage Line Regulation Flyback Amplifier Transconductance (gm) Flyback Amplifier Source and Sink Current Output Switch Breakdown Voltage Output Switch ON Resistance (Note 2, 4) Control Voltage to Switch Current Transconductance Switch Current Limit (LT1270) (Note 4) 3.0 10 1.08 1.25 0.54 UNITS V V nA nA µmho µmho µA µA V V %/V V/V V mA V V V 3000 2400 150 120 1.80 0.25 4400 500 800 2.8 7 0.90 6.8 17.6 18.0 8.5 V V V 0.01 0.03 %/V 150 300 650 µmho 15 25 60 32 40 75 70 70 µA µA V 0.12 0.18 0.22 Ω Ω A/V ● 3V ≤ VIN ≤ VMAX, VC = 0.6V Duty Cycle = 0 IFB = 50µA ● VFB TYP 1.244 1.244 350 0.05 ≤ IFB ≤ 1mA IFB = 50µA 3V ≤ VIN ≤ VMAX ∆lC = ±10µA VC = 0.6V Source IFB = 50µA Sink 3V ≤ VIN ≤ VMAX ISW = 1.5mA TJ ≤ 100°C TJ ≤ 125°C 200 0.38 ● ● Normal/Flyback Threshold on Feedback Pin Flyback Reference Voltage MIN 1.224 1.214 ● ● ● 0.70 0.50 0.40 15.0 14.0 4.5 0.45 16.3 MAX 1.264 1.274 750 1100 6000 7000 350 400 2.30 0.52 0.03 12 Duty Cycle = 50%, TJ ≤ 100°C Duty Cycle = 80%, TJ ≤ 100°C ● ● 8 6 16 14 A A 1270afc 2 LT1270A/LT1270 ELECTRICAL CHARACTERISTICS The ● denotes specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VIN = 15V, VC = 0.5V, VFB = VREF, switch pin open, unless otherwise noted. SYMBOL PARAMETER CONDITIONS ILIM Switch Current Limit (LT1270A) (Note 4) Supply Current Increase During Switch-ON Time Switching Frequency Duty Cycle = 50%, TJ ≤ 100°C Duty Cycle = 80%, TJ ≤ 100°C ∆IIN ∆ISW f MIN ● ● ● DCMAX Maximum Switch Duty Cycle Flyback Sense Delay Time Shutdown Mode Supply Current Shutdown Mode Threshold Voltage 3V ≤ VIN ≤ VMAX, VC = 0.05V 3V ≤ VIN ≤ VMAX ● Note 1: Absolute Maximum Ratings are those values beyond which the life of a device may be impaired. Note 2: Measured with VC in Hi Clamp, VFB = 0.8V. Note 3: For duty cycles (DC) between 50% and 80%, minimum guaranteed TYP MAX UNITS 25 16.0 14.0 40 A A mA/A 10.0 7.5 50 50 80 100 50 60 92 1.5 100 150 70 70 95 400 250 300 kHz kHz % µs µA mV mV switch current is given by ILIM = 6.67 (1.7 – DC) for the LT1270 and ILIM = 8.33 (1.7 – DC) for the LT1270A. Note 4: Minimum current limit is reduced by 0.5A at 125°C. 100°C test limits are guaranteed by correlation to 125°C tests. U W TYPICAL PERFOR A CE CHARACTERISTICS Switch Current Limit vs Duty Cycle Switch Saturation Voltage 24 1.6 SWITCH SATURATION VOLTAGE (V) SWITCH CURRENT (A) TJ = 25°C 18 –55°C 25°C 12 125°C 6 0 0 20 60 40 DUTY CYCLE (%) 80 1.2 0.8 0.4 0 100 0 2 6 8 4 SWITCH CURRENT (A) LT1270 • TA03 U TYPICAL APPLICATIO S 10 LT1270 • TA04 Boost Converter (5V to 12V) 5V VIN 55µH* VSW MBR1020 12V, 2A LT1270 10.7k FB GND + 1000µF VC 25V 1k 1.24k + 1µF PULSE ENGINEERING #PE-92116 LT1270 • TA05 1270afc Information furnished by Linear Technology Corporation is believed to be accurate and reliable. However, no responsibility is assumed for its use. Linear Technology Corporation makes no representation that the interconnection of circuits as described herein will not infringe on existing patent rights. 3 LT1270A/LT1270 U TYPICAL APPLICATIO S Negative-to-Positive Buck-Boost Converter Negative Buck Converter L2 OPTIONAL OUTPUT FILTER L1 55µH** VIN + OPTIONAL INPUT FILTER C3 + D1 VSW + LT1270 C2 2000µF + C4 200µF* OPTIONAL INPUT FILTER L3 10µH FB GND VC R3 2.2k C1 0.22µF L3 VIN –12V VIN VOUT 12V, 3A R1 11.3k 1.24k D1 L1 100µH** C2 1000µF –5.2V, 7.5A VSW 12k LT1270 C3 100µF* FB GND VC C1 OPTIONAL OUTPUT FILTER R2 1.24k R3 VIN –20V LT1270 • TA06 R1 4.64k LOAD 200µF L2 4µF LT1270 • TA07 *REQUIRED IF INPUT LEADS ≥ 2" **PULSE ENGINEERING #PE-92116 + C4 *REQUIRED IF INPUT LEADS ≥ 2" **PULSE ENGINEERING #PE-92115 U PACKAGE DESCRIPTIO T Package 5-Lead Plastic TO-220 (Standard) (Reference LTC DWG # 05-08-1421) .165 – .180 (4.191 – 4.572) .147 – .155 (3.734 – 3.937) DIA .390 – .415 (9.906 – 10.541) .045 – .055 (1.143 – 1.397) .230 – .270 (5.842 – 6.858) .570 – .620 (14.478 – 15.748) .460 – .500 (11.684 – 12.700) .330 – .370 (8.382 – 9.398) .620 (15.75) TYP .700 – .728 (17.78 – 18.491) SEATING PLANE .152 – .202 .260 – .320 (3.861 – 5.131) (6.60 – 8.13) .095 – .115 (2.413 – 2.921) .155 – .195* (3.937 – 4.953) .013 – .023 (0.330 – 0.584) BSC .067 (1.70) .028 – .038 (0.711 – 0.965) .135 – .165 (3.429 – 4.191) * MEASURED AT THE SEATING PLANE T5 (TO-220) 0801 RELATED PARTS PART NUMBER DESCRIPTION COMMENTS LT1074/HV 4.4A (IOUT), 100kHz, High Efficiency Step-Down DC/DC Converter VIN: 7.3V to 45/64V, VOUT (min) = 2.21V, IQ = 8.5mA, ISD = 10µA, DD-5/7, TO220-5/7 LTC3414 4A (IOUT), 4MHz, Synchronous Step-Down DC/DC Converter VIN: 2.3V to 5.5V, VOUT (min) = 0.8V, IQ = 64µA, ISD