LT3825 Isolated No-Opto Synchronous Flyback Controller with Wide Input Supply Range FEATURES DESCRIPTION n Senses Output Voltage Directly from Primary Side The LT 3825 is an isolated switching regulator controller designed for medium power flyback topologies. A typical WindingNo Opto-Isolator Required n application is 10W to 60W with input voltage limited only Synchronous Driver for High Efficiency n by external power path components. A third transformer Input Voltage Limited Only by External winding provides output voltage feedback. Power Components n Accurate Output Regulation without User Trims The LT3825 is a current mode controller that regulates n Switching Frequency from 50kHz to 250kHz output voltage based on sensing secondary voltage via a n Synchronizable transformer winding during flyback. This allows for tight n Load Compensation output regulation without the use of an opto-isolator, n Programmable Undervoltage Lockout improving dynamic response and reliability. Synchronous n Available in a Thermally Enhanced 16-Lead rectification increases converter efficiency and improves TSSOP Package output cross regulation in multiple output converters. The LT3825 operates in forced continuous conduction APPLICATIONS mode which improves cross regulation in multiple winding n applications. Switching frequency is user programmable Isolated Medium Power (10W to 60W) Supplies n and can be externally synchronized. The part also has load Isolated Telecom, Medical Converters n compensation, undervoltage lockout and soft-start circuity. Instrumentation Power Supplies n L, LT, LTC, LTM, Burst Mode, SwitcherCAD, Linear Technology and the Linear logo are registered Isolated Power over Ethernet Supplies trademarks and No R , ThinSOT are trademarks of Linear Technology Corporation. All other SENSE trademarks are the property of their respective owners. Protected by U.S. Patents, including 6948466, 5841643. Efficiency 92 TYPICAL APPLICATION 90 36V IN 48V IN 88 72V IN 86 48V to 3.3V at 12A Isolated Supply 84 + V + OUT V IN 82 3.3V 36V TO 72V 470F 12A 100pF 4 T1 80 28.7k T1 20 20 47k 78 47 2 3 4 5 6 7 8 9 10 11 12 3.01k + LOAD CURRENT (A) 3825 TA01b 47F SG 402k 2 Regulation + FB V SG PG SENSE 3.43 CC 2.2F SG 1F 0.02 UVLO 3.38 330 15 LT3825 SENSE 15k 36V IN 48V 2.2nF IN PGDLY V C 0.1F 3.33 72V IN t SYNC R ENDLY OSC GND SFST C ON CMP CMP 10nF 3.28 0.22F 10k 12k 100k 2.1k 150k 100k 47pF 0.1F 3.23 3825 TA01a 3.18 3.13 2 3 4 5 6 7 8 9 10 11 12 LOAD CURRENT (A) 3825 TA01c 3825fe 1 OUTPUT (V) EFFICIENCY (%)LT3825 ABSOLUTE MAXIMUM RATINGS PIN CONFIGURATION (Note 1) TOP VIEW V to GND CC Low Impedance Source ........................ 0.3V to 18V SG 1 16 PG Current Fed V 2 15 PGDLY CC t 3 14 R (V Has Internal 19.5V Clamp) ...........30mA Into V ON CMP CC CC ENDLY 4 13 C CMP UVLO, SYNC Pin Voltage ........................... 0.3V to V 17 CC GND + + SYNC 5 12 SENSE SENSE , SENSE Pin Voltage ......................0.5V, +0.5V SFST 6 11 SENSE FB Pin Current ........................................................2mA OSC 7 10 UVLO V Pin Current ....................................................... 1mA C FB 8 9 V C Operating Junction Temperature Range FE PACKAGE (Notes 2, 3, 4) ........................................ 40C to 125C 16-LEAD PLASTIC TSSOP Storage Temperature Range ................. 65C to 150C T = 125C, = 40C/W, = 10C/W JMAX JA JC EXPOSED PAD (PIN 17) IS GND, MUST BE SOLDERED TO PCB Lead Temperature (Soldering, 10 sec) ...................300C ORDER INFORMATION LEAD FREE FINISH TAPE AND REEL PART MARKING PACKAGE DESCRIPTION TEMPERATURE RANGE LT3825EFE PBF LT3825EFE TRPBF 3825EFE 16-Lead Plastic 4.4mm TSSOP 40C to 125C LEAD BASED FINISH TAPE AND REEL PART MARKING PACKAGE DESCRIPTION TEMPERATURE RANGE LT3825EFE LT3825EFE TR 3825EFE 16-Lead Plastic 4.4mm TSSOP 40C to 125C Consult LTC Marketing for parts specified with wider operating temperature ranges. For more information on lead free part marking, go to: