LT1961 1.5A, 1.25MHz Step-Up Switching Regulator FEATURES DESCRIPTIO 1.5A Switch in a Small MSOP Package The LT 1961 is a 1.25MHz monolithic boost switching Constant 1.25MHz Switching Frequency regulator. A high efficiency 1.5A, 0.2 switch is included Wide Operating Voltage Range: 3V to 25V on the die together with all the control circuitry required to High Efficiency 0.2 Switch complete a high frequency, current-mode switching regu- 1.2V Feedback Reference Voltage lator. Current-mode control provides fast transient re- 2% Overall Output Voltage Tolerance sponse and excellent loop stability. Uses Low Profile Surface Mount External New design techniques achieve high efficiency at high Components switching frequencies over a wide operating voltage range. Low Shutdown Current: 6 A A low dropout internal regulator maintains consistent Synchronizable from 1.5MHz to 2MHz performance over a wide range of inputs from 24V sys- Current-Mode Loop Control tems to Li-Ion batteries. An operating supply current of Constant Maximum Switch Current Rating at All Duty 1mA maintains high efficiency, especially at lower output Cycles* currents. Shutdown reduces quiescent current to 6A. Thermally Enhanced Exposed Pad 8-Lead Plastic Maximum switch current remains constant at all duty MSOP Package cycles. Synchronization allows an external logic level U signal to increase the internal oscillator from 1.5MHz to APPLICATIO S 2MHz. DSL Modems The LT1961 is available in an exposed pad, 8-pin MSOP Portable Computers package. Full cycle-by-cycle switch current limit protec- Battery-Powered Systems tion and thermal shutdown are provided. High frequency Distributed Power operation allows the reduction of input and output filtering components and permits the use of chip inductors. , LT, LTC and LTM are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. *Patent Pending TYPICAL APPLICATIO Efficiency vs Load Current 5V to 12V Boost Converter 90 6.8H 85 UPS120 V OUT 1 2 80 V IN 12V V V IN SW 5V 0.5A* LT1961 2.2F 90.9k OPEN 75 CERAMIC OR 5 6 SHDN FB HIGH V SYNC GND C 70 = ON 8 3,4 7 10F 10k 6800pF CERAMIC 65 1% 100pF V = 5V IN 6.8k V = 12V OUT 60 0 100 200 300 400 500 *MAXIMUM OUTPUT CURRENT IS SUBJECT TO THERMAL DERATING. 1961 TA01 LOAD CURRENT (mA) 1961 TA01a 1961fa 1 EFFICIENCY (%) U ULT1961 ABSOLUTE MAXIMUM RATINGS PI CO FIGURATIO (Note 1) TOP VIEW Input Voltage .......................................................... 25V V 1 8 SYNC IN Switch Voltage ......................................................... 35V SW 2 7 V C SHDN Pin ............................................................... 25V GND 3 6 FB GND 4 5 SHDN FB Pin Current ....................................................... 1mA MS8E PACKAGE SYNC Pin Current .................................................. 1mA 8-LEAD PLASTIC MSOP Operating Junction Temperature Range (Note 2) GROUND PAD CONNECTED TO LARGE COPPER AREA LT1961E, LT1961I ........................... 40C to 125C T = 125C, = 50C/W JMAX JA Storage Temperature Range ................ 65C to 150C Lead Temperature (Soldering, 10 sec)................. 300C UUW ORDER I FOR ATIO LEAD FREE FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE LT1961EMS8E PBF LT1961EMS8E TRPBF LTQY 8-Lead Plastic MSOP 40C to 125C LT1961IMS8E PBF LT1961IMS8E TRPBF LTQY 8-Lead Plastic MSOP 40C to 125C LEAD BASED FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE LT1961EMS8E LT1961EMS8E TR LTQY 8-Lead Plastic MSOP 40C to 125C LT1961IMS8E LT1961IMS8E TR LTQY 8-Lead Plastic MSOP 40C to 125C Consult LTC Marketing for parts specified with wider operating temperature ranges. *Temperature grades are identified by a label on the shipping container. For more information on lead free part marking, go to: