LT1372/LT1377 500kHz and 1MHz High Efficiency 1.5A Switching Regulators FEATURES DESCRIPTIO n Faster Switching with Increased Efficiency The LT 1372/LT1377 are monolithic high frequency n Uses Small Inductors: 4.7m H switching regulators. They can be operated in all standard n All Surface Mount Components switching configurations including boost, buck, flyback, n Only 0.5 Square Inch of Board Space forward, inverting and Cuk. A 1.5A high efficiency switch n Low Minimum Supply Voltage: 2.7V is included on the die, along with all oscillator, control and n Quiescent Current: 4mA Typ protection circuitry. All functions of the LT1372/LT1377 n Current Limited Power Switch: 1.5A are integrated into 8-pin SO/PDIP packages. n Regulates Positive or Negative Outputs The LT1372/LT1377 typically consumes only 4mA quies- n Shutdown Supply Current: 12m A Typ cent current and has higher efficiency than previous parts. n Easy External Synchronization High frequency switching allows for very small inductors n 8-Pin SO or PDIP Packages to be used. All surface mount components consume less than 0.5 square inch of board space. U APPLICATIO S 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 CCFL Backlight Driver reduces supply current to 12m A. Unique error amplifier n Laptop Computer Supplies circuitry can regulate positive or negative output voltage n Multiple Output Flyback Supplies while maintaining simple frequency compensation tech- n Inverting Supplies 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 APPLICATIO 12V Output Efficiency 5V-to-12V Boost Converter 100 D1 5V V = 5V L1* IN MBRS120T3 4.7m H V OUT 90 12V 5 V R1 IN 4 8 53.6k ON V S/S SW 80 OFF 1% *FOR LT1372 USE 10H LT1372/LT1377 COILCRAFT DO1608-472 (4.7H) OR 2 + + COILCRAFT DT3316-103 (10H) OR FB C1** C4** 70 SUMIDA CD43-4R7 (4.7H) OR 22F 22m F GND V C SUMIDA CD73-100KC (10H) OR R2 **AVX TPSD226M025R0200 6, 7 1 60 6.19k MAX I OUT C2 1% 0.047m F L1 I (LT1377) I (LT1372) OUT OUT R3 C3 4.7m H 0.25A NA 50 2k 0.0047m F 0.01 0.1 1 10m H 0.35A 0.29A OUTPUT CURRENT (A) LT1372 TA01 LT1372 TA02 1 EFFICIENCY (%) U ULT1372/LT1377 UUW ABSOLUTE AXI U RATI GS PACKAGE/ORDER I FOR ATIO (Note 1) ORDER PART NUMBER Supply Voltage ....................................................... 30V TOP VIEW Switch Voltage LT1372CN8 LT1372HVIN8 V 1 V 8 C SW LT1372/LT1377 .................................................. 35V LT1372HVCN8 LT1372IS8 FB 2 7 GND LT1372HV .......................................................... 42V LT1372CS8 LT1372HVIS8 NFB 3 6 GND S S/S Pin Voltage ....................................................... 30V LT1372HVCS8 LT1377CS8 S/S 4 5 V IN Feedback Pin Voltage (Transient, 10ms) .............. 10V LT1372IN8 LT1377IS8 N8 PACKAGE S8 PACKAGE Feedback Pin Current........................................... 10mA 8-LEAD PDIP 8-LEAD PLASTIC SO S8 PART MARKING Negative Feedback Pin Voltage T = 125 C, q = 100 C/ W (N8) JMAX JA (Transient, 10ms) ............................................. 10V 1372 1372H 1377 T = 125 C, q = 120 C/ W (S8) JMAX JA Operating Junction Temperature Range 1377I 1372I 1372HI Commercial ........................................ 0 C to 125 C* Consult factory for parts specified with wider operating temperature ranges. Industrial ......................................... 40 C to 125 C *Units shipped prior to Date Code 9552 are rated at 100 C maximum Short Circuit ......................................... 0 C to 150 C operating temperature. Storage Temperature Range ................ 65 C to 150 C Lead Temperature (Soldering, 10 sec)................. 300 C ELECTRICAL CHARACTERISTICS The l denotes specifcatons which appy over the full operating temperature range, otherwise specifications are at T = 25 C. A V = 5V, V = 0.6V, V = V , V , S/S 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 V Negative Feedback Reference Voltage Measured at Negative Feedback Pin 2.540 2.490 2.440 V NFB Feedback Pin Open, V = 0.8V l 2.570 2.490 2.410 V C I Negative Feedback Input Current V = V l 45 30 15 m A NFB NFB NFR Negative Feedback Reference Voltage 2.7V V 25V, V = 0.8V l 0.01 0.05 %/V IN C Line Regulation g Error Amplifier Transconductance D I = 25m A 1100 1500 1900 m mho m C l 700 2300 m mho Error Amplifier Source Current V = V 150mV, V = 1.5V l 120 200 350 m A FB REF C Error Amplifier Sink Current V = V + 150mV, V = 1.5V l 1400 2400 m A FB REF C Error Amplifier Clamp Voltage High Clamp, V = 1V 1.70 1.95 2.30 V FB Low Clamp, V = 1.5V 0.25 0.40 0.52 V FB A Error Amplifier Voltage Gain 500 V/V V V Pin Threshold Duty Cycle = 0% 0.8 1 1.25 V C f Switching Frequency 2.7V V 25V IN LT1372 450 500 550 kHz 0 C T 125 C l 430 500 580 kHz J 40 C T < 0 C (I Grade) 400 580 kHz J LT1377 0.90 1 1.10 MHz 0 C T 125 C l 0.86 1 1.16 MHz J 40 C T < 0 C (I Grade) 0.80 1.16 MHz J 2 U WWW