POWER LOSS (W) LT3844 High Voltage, Current Mode Switching Regulator Controller with Programmable Operating Frequency Fea T Descrip T n High Voltage Operation: Up to 60V The LT 3844 is a DC/DC controller used for medium power, n Output Voltages Up to 36V (Step Down) low part count, high efficiency supplies. It offers a wide n Programmable Constant Frequency: 100kHz to 4V to 60V input range (7.5V minimum start-up voltage) 500kHz and can implement step-down, step-up, inverting and n Synchronizable up to 600kHz SEPIC topologies. n Burst Mode Operation: 120A Supply Current The LT3844 includes Burst Mode operation, which reduces n 10A Shutdown Supply Current quiescent current below 120A and maintains high effi- n 1.3% Reference Accuracy ciency at light loads. An internal high voltage bias regulator n Drives N-Channel MOSFET allows for simple biasing. n Programmable Soft-Start n Additional features include current mode control for fast Programmable Undervoltage Lockout n line and load transient response programmable fixed Internal High Voltage Regulator for Gate Drive n operating frequency that can be synchronized to an ex- Thermal Shutdown n ternal clock for noise sensitive applications a gate driver Current Limit Unaffected by Duty Cycle n capable of driving large N-channel MOSFETs a precision 16-Pin Thermally Enhanced TSSOP Package undervoltage lockout function 10A shutdown current short-circuit protection and a programmable soft-start a T function. n Industrial Power Distribution The LT3844 is available in a 16-lead thermally enhanced n 12V and 42V Automotive and Heavy Equipment TSSOP package. n High Voltage Single Board Systems L, LT, LTC and LTM are registered trademarks of Linear Technology Corporation. n Distributed Power Systems Burst Mode is a registered trademark of Linear Technology Corporation. All other trademarks are the property of their respective owners. n Avionics Protected by U.S. Patents, including 5731694, 6498466, 6611131 n Telecom Power Typical a T High Voltage Step-Down Regulator 48V to 12V, 50W Efficiency and Power Loss vs Load Current V IN 36V TO 60V 68F 22F 0.22F 90 7 V = 48V IN 1M V BOOST IN 88 6 SHDN TG Si7850DP 1000pF 86 5 10 EFFICIENCY 82.5k C SW SS 84 4 BURST EN V CC 10H V 0.015 OUT 82 3 1F LT3844 12V LOSS V PGND 50W FB 68F PDS5100H 80 2 10k 14.7k 33F + V SENSE C 78 1 680p 120pF SYNC SENSE 76 0 130k 0.1 1 10 f SGND SET LOAD CURRENT (A) R7 3844 TA01b 49.9k 3844 TA01 3844fc 1 For more information www.linear.com/LT3844 EFFICIENCY (%) ion pplica ions pplica ion uresLT3844 a Te Maxi Mu M r a T p in c F T (Note 1) TOP VIEW Input Supply Voltage (V ) ......................... 65V to 0.3V IN Boosted Supply Voltage (BOOST) .............. 80V to 0.3V V 1 16 BOOST IN SHDN 2 15 TG Switch Voltage (SW) (Note 8) ........................65V to 1V C 3 14 SW SS Differential Boost Voltage BURST EN 4 13 V CC BOOST to SW ........................................ 24V to 0.3V 17 V 5 12 PGND FB Bias Supply Voltage (V ) .......................... 24V to 0.3V CC + V 6 11 SENSE + C SENSE and SENSE Voltages ................... 40V to 0.3V SYNC 7 10 SENSE Differential Sense Voltage f 8 9 SGND SET + SENSE to SENSE ......................................1V to 1V FE PACKAGE BURST EN Voltage .................................... 24V to 0.3V 16-LEAD PLASTIC TSSOP SYNC, V , V , C and SHDN Voltages ...... 5V to 0.3V T = 125C, = 40C/W, = 10C/W C FB SS JMAX JA JC EXPOSED PAD (PIN 17) IS SGND, MUST BE SOLDERED TO PCB SHDN Pin Currents ..................................................1mA Operating Junction Temperature Range (Note 2) LT3844E (Note 3) .............................. 40C to 125C LT3844I ............................................. 40C to 125C Storage Temperature.............................. 65C to 150C Lead Temperature (Soldering, 10 sec) ...................300C o r Der i n F Ma T