LTC3766 High Efficiency, Secondary-Side Synchronous Forward Controller FEATURES DESCRIPTION n Direct Flux Limit Guarantees No Saturation The LTC 3766 is a PolyPhase-capable secondary-side n Fast and Accurate Average Current Limit controller for synchronous forward converters. When used n Clean Start-Up Into Pre-Biased Output in conjunction with the LTC3765 active-clamp forward n Secondary-Side Control for Fast Transient Response controller and gate driver, the part creates a complete n Simple, Self-Starting Architecture isolated power supply that combines the power of multi- n Synchronous MOSFET Reverse Current Limit phase operation with the speed of secondary-side control. n PolyPhase Operation Eases High-Power Design The LTC3766 has been designed to simplify the design of n True Remote Sense Differential Amplifier active clamp forward converters. Working in concert with n Remote Sense Reverse Protection the LTC3765, the LTC3766 forms a robust, self-starting n High Voltage Linear Regulator Controller converter that eliminates the need for the separate bias n Internal LDO Powers Gate Drive from V OUT regulator that is commonly used in secondary-side control n Overtemperature/Overvoltage Protection applications. A precision current-limit coupled with clean n Low Profile 4mm 5mm QFN and Narrow 28-Lead start-up into a pre-biased load make the LTC3766 an excel- SSOP Packages lent choice for high-power battery charger applications. APPLICATIONS The LTC3766 provides extensive remote sensing and output protection features, while Direct Flux Limit guarantees no n Isolated 48V Telecommunication Systems transformer saturation without compromising transient n Isolated Battery Chargers response. A linear regulator controller and internal bypass n Automotive and Military Systems LDO are also provided to simplify the generation of the n Industrial, Avionics and Heavy Equipment secondary-side bias voltage. L, LT, LTC, LTM, PolyPhase, Linear Technology and the Linear logo are registered and Direct Flux Limit is a trademark of Linear Technology Corporation. All other trademarks are the property of their respective owners. Protected by U.S. Patents, including 7200014 and 6144194. Other patents pending. TYPICAL APPLICATION 36V 72V to 5V/15A Active Clamp Isolated Forward Converter 1.4H +V OUT +V IN 6:2 5V 36V TO 72V 15A EFFICIENCY: 94% AT 48V /15A IN OUT 2.2F 220F 100V FDMS86201 6.3V BSC0901NS SiR414DP 3 33nF 100nF 2 200V 200V 15m 3m 168 0.5W 2W V IN V OUT 2.2nF Si3437DV 200k (SOT23) 250VAC Si3440DV + 1 FG SW SG RUN V NDRV V FS/SYNC V V IN CC S S 4.42k I S + 365k 0.1F 1.0F + NDRV PG I I AG I I FB S S SMAG S 2:1 + + LTC3766 RUN IN PT ITH 604 LTC3765 PT V CC IN SS SSFLT FS/UV 470pF 4.7F GND PGND I SGD FGD MODE PK R CORE DELAY SGND PGND 33nF 26.1k 15k 22.1k 17.8k 47pF 15.0k 33nF 10.5k 14k 18.2k 3766 TA01 3766fc 1 For more information www.linear.com/LTC3766LTC3766 ABSOLUTE MAXIMUM RATINGS (Note 1) V Voltage .................................................0.3V to 12V V Voltage ................................................ 0.3V to 3V CC SEC V Voltage ................................................. 0.3V to 33V I , SS Voltages ........................................... 0.3V to 4V IN PK RUN Voltage............................................... 0.3V to 33V Operating Junction Temperature Range (Notes 2,3) SW LTC3766E, LTC3766I ......................... 40C to 125C Low Impedance Source ............................ 5V to 40V LTC3766H .......................................... 40C to 150C Current Fed .......... 2mA DC or 0.2A for <1s Into Pin* LTC3766MP ....................................... 55C to 150C + V , V , V , V , NDRV Voltages ...... 0.3V to 16V Storage Temperature Range .................. 65C to 150C AUX S S SOUT + ITH, I , REGSD Voltages ............................ 0.3V to 6V Lead Temperature (Soldering, 10 sec ) S PHASE Voltage ............................................. 0.3V to 6V GN Package .....................................................300C I , SGD, FGD Voltages ...............................0.3V to 12V S *The LTC3766 contains an internal 50V clamp that limits the voltage on the FS/SYNC, FB, MODE Voltages .....................0.3V to 12V SW pin. PIN CONFIGURATION TOP VIEW TOP VIEW 1 28 V SG CC 2 27 PGND FG 28 27 26 25 24 23 + 3 26 PT V SEC MODE 1 22 PT 4 25 PT MODE PHASE 2 21 V AUX 5 24 V PHASE AUX FB 3 20 SW 6 23 SW FB ITH 4 19 V 29 IN 7 22 V ITH GND IN RUN 5 18 NDRV 8 21 NDRV RUN SS 6 17 FGD 9 20 FGD SS I 7 16 SGD PK + 10 19 SGD I V 8 15 I PK SOUT S + 11 18 I 9 10 11 12 13 14 V SOUT S + 12 17 I V S S 13 16 REGSD V S 14 15 FS/SYNC GND UFD PACKAGE 28-LEAD (4mm 5mm) PLASTIC QFN GN PACKAGE T = 125C, = 43C/W JMAX JA 28-LEAD NARROW PLASTIC SSOP EXPOSED PAD (PIN 29) IS GND, MUST BE SOLDERED TO PCB T = 125C, = 95C/W JMAX JA 3766fc 2 For more information www.linear.com/LTC3766 + V V S SEC V FG S GND SG FS/SYNC V CC REGSD PGND + I PT S