LT8309 Secondary-Side Synchronous Rectifier Driver Fea T Descrip T n Works with DCM and BCM/CrCM Conduction Mode The LT 8309 is a secondary-side synchronous rectifier Flyback Topologies driver that replaces the output rectifier diode in a flyback n V : 4.5V to 40V topology. By replacing the diode with a N-channel MOSFET, CC n Supports Up to 150V MOSFETs applications are no longer restricted by the heat constraints n 26ns Turn-Off Propagation Delay of the output diode. The IC replicates the behavior of a n Accurate Minimum On and Off Timers for Reliable diode by sensing the drain-to-source voltage to determine Operation when the current becomes negative. The LT8309 s low n Adjustable and Accurate Trip Point: +5mV to 30mV minimum on- and off-times help improve noise immunity. n 1 Gate Driver Pull-Down The fast propagation delay of 26ns allows applications to n SOT-23 5-Lead Package operate in discontinuous conduction mode (DCM) and critical conduction mode (CrCM). The gate driver features a T a 0.8 pull-down device for fast turn-offs. The 40V V CC rating allows the part to be driven from the output volt- n High Output Current Flybacks age or the rectified drain voltage of the MOSFET. A low n High Efficiency Flybacks quiescent current of 400A maximizes efficiency at low output currents. L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. Typical a T 40W, 5V Isolated Telecom Supply Efficiency vs Load Current 5.33:1 100 + V IN V OUT 36V TO 5V, 8A 10F 412k 60 400F 72V 95 V EN/UVLO IN V = 48V WITH LT8309 10 LT8309 IN 100pF 90 15.4k V CC LT3748 147k 1F R FB 85 R REF 6.2V V = 48V WITH PDS760 DIODE 2.2k IN 6.04k 80 DRAIN INTV CC TC GATE GATE 75 GND SS SENSE 70 30.9k V GND INTV C CC 4.7F 12m V OUT 12.1k 65 0.1F 4.7F 0 1 2 3 4 5 6 7 8 8309 TA01a 15nF LOAD CURRENT (A) 8309 TA01b 8309fa 1 For more information www.linear.com/LT8309 EFFICIENCY (%) ion pplica ions pplica ion uresLT8309 a Te Maxi Mu M r a T p c F T (Note 1) V ............................................................................40V TOP VIEW CC INTV GATE ............................................................10V CC GATE 1 5 DRAIN DRAIN .....................................................................150V GND 2 Maximum Junction Temperature .......................... 125C INTV 3 4 V CC CC Operating Temperature Range (Note 2) S5 PACKAGE 5-LEAD PLASTIC TSOT-23 LT8309E ............................................ 40C to 125C = 215C/W JA LT8309I ............................................. 40C to 125C LT8309H ............................................ 40C to 150C Storage Temperature Range .................. 65C to 150C o r D i n F Ma T LEAD FREE FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE LT8309ES5 PBF LT8309ES5 TRPBF LTGFZ 5-Lead Plastic TSOT-23 40C to 125C LT8309IS5 PBF LT8309IS5 TRPBF LTGFZ 5-Lead Plastic TSOT-23 40C to 125C LT8309HS5 PBF LT8309HS5 TRPBF LTGFZ 5-Lead Plastic TSOT-23 40C to 150C Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container. For more information on lead free part marking, go to: