LT1956/LT1956-5 High Voltage, 1.5A, 500kHz Step-Down Switching Regulators FEATURES DESCRIPTIO n Wide Input Range: 5.5V to 60V The LT 1956/LT1956-5 are 500kHz monolithic buck n 1.5A Peak Switch Current switching regulators with an input voltage capability up to n Small 16-Pin SSOP or Thermally Enhanced 60V. A high efficiency 1.5A, 0.2W switch is included on the TSSOP Package die along with all the necessary oscillator, control and logic n Saturating Switch Design: 0.2W circuitry. A current mode architecture provides fast tran- n Peak Switch Current Maintained Over sient response and good loop stability. Full Duty Cycle Range Special design techniques and a new high voltage process n Constant 500kHz Switching Frequency achieve high efficiency over a wide input range. Efficiency n Effective Supply Current: 2.5mA is maintained over a wide output current range by using the n Shutdown Current: 25m A output to bias the circuitry and by utilizing a supply boost n 1.2V Feedback Reference (LT1956) capacitor to saturate the power switch. Patented circuitry n 5V Fixed Output (LT1956-5) maintains peak switch current over the full duty cycle n Easily Synchronizable range*. A shutdown pin reduces supply current to 25m A and n Cycle-by-Cycle Current Limiting the device can be externally synchronized from 580kHz to U 700kHz with a logic level input. APPLICATIO S The LT1956/LT1956-5 are available in fused-lead 16-pin n High Voltage, Industrial and Automotive SSOP and thermally enhanced TSSOP packages. n Portable Computers , LTC and LT are registered trademarks of Linear Technology Corporation. n Battery-Powered Systems *U.S. PATENT NO. 6,498,466 n Battery Chargers n Distributed Power Systems TYPICAL APPLICATIO 5V Buck Converter Efficiency vs Load Current MMSD914TI 100 V = 12V IN 6 L = 18H V = 5V 0.1F OUT V BOOST 90 IN 10H V OUT 12V 4 2 V SW 5V IN (TRANSIENTS V = 3.3V OUT 2.2F 1A TO 60V) 10MQ060N 80 100V LT1956-5 22F CERAMIC 6.3V 15 10 CERAMIC SHDN BIAS 70 14 12 SYNC FB 60 GND V C 1, 8, 9, 16 11 50 0 0.25 0.50 0.75 1.00 1.25 220pF 4.7k LOAD CURRENT (A) 1956 TA02 4700pF UNITED CHEMI-CON THCS50EZA225ZT 1956 TA01 1956f 1 EFFICIENCY (%) U ULT1956/LT1956-5 ABSOLUTE AXI U RATI GS (Note 1) Input Voltage (V ) ................................................. 60V Operating Junction Temperature Range IN BOOST Pin Above SW ............................................ 35V LT1956EFE/LT1956EFE-5/LT1956EGN/LT1956EGN-5 BOOST Pin Voltage ................................................. 68V (Notes 8, 10) ..................................... 40 C to 125 C SYNC, SENSE Voltage (LT1956-5) ........................... 7V LT1956IFE/LT1956IFE-5/LT1956IGN/LT1956IGN-5 SHDN Voltage ........................................................... 6V (Notes 8, 10) ..................................... 40 C to 125 C BIAS Pin Voltage .................................................... 30V Storage Temperature Range ................ 65 C to 150 C FB Pin Voltage/Current (LT1956) ................... 3.5V/2mA Lead Temperature (Soldering, 10 sec)................. 300 C UUW PACKAGE/ORDER I FOR ATIO TOP VIEW TOP VIEW ORDER PART ORDER PART GND 1 16 GND NUMBER NUMBER GND 1 16 GND SW 2 15 SHDN SW 2 15 SHDN LT1956EGN LT1956EFE NC 3 14 SYNC NC 3 14 SYNC LT1956IGN LT1956IFE V 4 13 NC IN V 4 13 NC IN LT1956EGN-5 LT1956EFE-5 NC 5 12 FB/SENSE NC 5 12 FB/SENSE LT1956IGN-5 LT1956IFE-5 BOOST 6 11 V C BOOST 6 11 V C NC 7 10 BIAS NC 7 10 BIAS FE PART MARKING GN PART MARKING GND 8 9 GND GND 8 9 GND 1956EFE 1956 FE PACKAGE GN PACKAGE 16-LEAD PLASTIC TSSOP 16-LEAD PLASTIC SSOP 1956IFE 1956I T = 125 C, q = 45 C/ W, q (PAD) = 10 C/ W JMAX JA JC T = 125 C, q = 85 C/ W, q (PIN 8) = 25 C/ W JMAX JA JC 19565 1956EFE-5 EXPOSED BACKSIDE MUST BE SOLDERED FOUR CORNER PINS SOLDERED TO GROUND PLANE 1956IFE-5 1956I5 TO GROUND PLANE Consult LTC Marketing for parts specified with wider operating temperature ranges. ELECTRICAL CHARACTERISTICS The l denotes specifications which apply over the full operating temperature range, otherwise specifications are at T = 25 C. J V = 15V, V = 1.5V, SHDN = 1V, Boost o/c, SW o/c, unless otherwise noted. IN C PARAMETER CONDITIONS MIN TYP MAX UNITS Reference Voltage (LT1956) 5.5V V 60V 1.204 1.219 1.234 V IN V + 0.2 V V 0.2 l 1.195 1.243 V OL C OH SENSE Voltage (LT1956-5) 5.5V V 60V 4.94 5 5.06 V IN V + 0.2 V V 0.2 l 4.90 5.10 V OL C OH SENSE Pin Resistance (LT1956-5) 9.5 13.8 19 kW FB Input Bias Current (LT1956) l 0.5 1.5 m A Error Amp Voltage Gain (Notes 2, 9) 200 400 V/V Error Amp g dl (V ) = 10m A (Note 9) 1500 2000 3000 m Mho m C l 1000 3200 m Mho V to Switch g 1.7 A/V C m EA Source Current FB = 1V or V = 4.1V l 125 225 400 m A SENSE EA Sink Current FB = 1.4V or V = 5.7V l 100 225 450 m A SENSE V Switching Threshold Duty Cycle = 0 0.9 V C V High Clamp SHDN = 1V 2.1 V C 1956f 2 U WWW