LT1373 250kHz Low Supply Current High Efficiency 1.5A Switching Regulator FEATURES DESCRIPTIO n 1mA I at 250kHz The LT 1373 is a low supply current high frequency Q n Uses Small Inductors: 15m H current mode switching regulator. It can be operated in all n All Surface Mount Components standard switching configurations including boost, buck, n Only 0.6 Square Inch of Board Space flyback, forward, inverting and Cuk. A 1.5A high effi- n Low Minimum Supply Voltage: 2.7V ciency switch is included on the die, along with all oscilla- n Constant Frequency Current Mode tor, control and protection circuitry. All functions of the n Current Limited Power Switch: 1.5A LT1373 are integrated into 8-pin SO/PDIP packages. n Regulates Positive or Negative Outputs Compared to the 500kHz LT1372, which draws 4mA of n Shutdown Supply Current: 12m A Typ quiescent current, the LT1373 switches at 250kHz, typi- n Easy External Synchronization cally consumes only 1mA and has higher efficiency. High n 8-Pin SO or PDIP Packages frequency switching allows for small inductors to be used. All surface mount components consume less than 0.6 U square inch of board space. APPLICATIO S New design techniques increase flexibility and maintain n Boost Regulators ease of use. Switching is easily synchronized to an exter- n CCFL Backlight Driver nal logic level source. A logic low on the shutdown pin n Laptop Computer Supplies reduces supply current to 12m A. 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 APPLICATIO 12V Output Efficiency 5V-to-12V Boost Converter 100 V = 5V IN D1 5V L1* f = 250kHz MBRS120T3 22m H V 90 OUT 12V 5 R1 V 215k IN 4 8 80 ON 1% V S/S SW OFF + C4** LT1373 22m F 2 70 + FB C1** MAX I OUT 22m F GND V C L1 I OUT 60 R2 6, 7 1 15m H 0.3A 24.9k C2 22m H 0.35A 1% 0.01m F *SUMIDA CD75-220KC (22m H) OR 50 R3 COILCRAFT D03316-153 (15m H) 1 10 100 1000 5k ** AVX TPSD226M025R0200 OUTPUT CURRENT (mA) LT1373 TA01 LT1373 TA02 1 EFFICIENCY (%) U ULT1373 UUW ABSOLUTE AXI U RATI GS PACKAGE/ORDER I FOR ATIO (Note 1) Supply Voltage ....................................................... 30V ORDER PART TOP VIEW NUMBER Switch Voltage V 1 8 V LT1373 ............................................................... 35V C SW LT1373CN8 LT1373IN8 FB 2 GND 7 LT1373HV .......................................................... 42V LT1373HVCN8 LT1373HVIN8 NFB 3 6 GND S S/S Pin Voltage ....................................................... 30V LT1373CS8 LT1373IS8 S/S 4 5 V IN Feedback Pin Voltage (Transient, 10ms) .............. 10V LT1373HVCS8 LT1373HVIS8 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 T = 125 C, q = 120 C/ W (S8) JMAX JA (Transient, 10ms) ............................................. 10V 1373 1373H Operating Junction Temperature Range 1373I 1373HI Commercial ........................................ 0 C to 125 C* Consult factory for Military grade parts. 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 specifications which apply 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 50 150 nA FB FB REF l 275 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 2.51 2.45 2.39 V NFB Feedback Pin Open, V = 0.8V l 2.55 2.45 2.35 V C I Negative Feedback Input Current V = V l 12 7 2 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 = 5m A 250 375 500 m mho m C l 150 600 m mho Error Amplifier Source Current V = V 150mV, V = 1.5V l 25 50 90 m A FB REF C Error Amplifier Sink Current V = V + 150mV, V = 1.5V l 850 1500 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 250 V/V V V Pin Threshold Duty Cycle = 0% 0.8 1 1.25 V C f Switching Frequency 2.7V V 25V 225 250 275 kHz IN 0 C T 125 C l 210 250 290 kHz J 40 C T 0 C (I Grade) 200 290 kHz J Maximum Switch Duty Cycle l 85 95 % Switch Current Limit Blanking Time 340 500 ns 2 U WWW