LT3837 Isolated No-Opto Synchronous Flyback Controller FEATURES DESCRIPTION n Senses Output Voltage Directly from Primary Side The LT 3837 is an isolated switching regulator controller WindingNo Optoisolator Required designed for medium power flyback topologies. A typical n Synchronous Driver for High Efficiency application is 10W to 60W with the part powered from a n Supply Voltage Range 4.5V to 20V DC supply. n Accurate Regulation Without User Trims The LT3837 is a current mode controller that regulates an n Programmable Switching Frequency from output voltage based on sensing the secondary voltage 50kHz to 250kHz via a transformer winding during flyback. This allows for n Synchronizable tight output regulation without the use of an optoisolator, n Load Compensation improving dynamic response and reliability. Synchronous n Undervoltage Lockout rectification increases converter efficiency and improves n Available in a Thermally Enhanced 16-Lead output cross regulation in multiple output converters. TSSOP Package The LT3837 operates in forced continuous conduction mode which improves cross regulation in multiple winding APPLICATIONS applications. Switching frequency is user programmable n Isolated Medium Power (10W to 60W) Supplies and can be externally synchronized. The part also has load n Instrumentation Power Supplies compensation, undervoltage lockout and soft-start circuitry. n Isolated Medical Supplies The LT3837 is available in a thermally enhanced 16-pin 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. TSSOP package. Protected by U.S. Patents including 6498466, 5841643. Efficiency vs Load Current TYPICAL APPLICATION 90 18V 9V IN IN 88 9V 18V to 3.3V at 10A Isolated Converter 86 V IN 22.1k 84 10F 82 BAS16 100nH OUTPUT 3.3V/10A 2N3906 80 22F 47F 3 220F 2.2nF V 86.6k CC 78 10 FB UVLO 76 B0540W V C 2 3 4 5 6 7 8 9 10 3k 1nF 15k 10 LT3837 3837 TA01b 47pF LOAD CURRENT (A) 20k OSC FMMT618 1F Regulation vs Load Current Si7336ADP 3.3nF SFST 3.60 PG Si7852DP 100k FMMT718 t ON + 150k SENSE 3.50 ENDLY 12k 8m PGDLY 3.40 1.37k SENSE R 0.1F 2.2nF CMP 9V IN 330 15 0.1F SG 3.30 C CMP 18V IN GND 10k BAT54 3.20 3837 TA01a 3.10 3.00 2 3 4 5 6 7 8 9 10 3837 TA01c LOAD CURRENT (A) 3837fd 1 OUTPUT (V) EFFICIENCY (%)LT3837 ABSOLUTE MAXIMUM RATINGS PIN CONFIGURATION (Note 1) TOP VIEW V to GND ................................................ 0.3V to 22V CC SG 1 16 PG UVLO, SYNC Pin Voltage ............................0.3V to V CC + V 2 15 PGDLY CC SENSE , SENSE Pin Voltage ......................0.5V, +0.5V t 3 14 R ON CMP FB Pin Current ....................................................... 2mA ENDLY 4 13 C CMP 17 V Pin Current ....................................................... 1mA C + SYNC 5 12 SENSE Operating Junction Temperature Range SFST 6 11 SENSE (Notes 2, 3, 4) ........................................ 40C to 125C OSC 7 10 UVLO Storage Temperature Range ..................65C to 150C FB 8 9 V C Lead Temperature (Soldering, 10 sec) ...................300C FE PACKAGE 16-LEAD PLASTIC TSSOP T = 125C, q = 40C/W, q = 10C/W JMAX JA JC EXPOSED PAD (PIN 17) IS GND,MUST BE SOLDERED TO PCB ORDER INFORMATION LEAD FREE FINISH TAPE AND REEL PART MARKING PACKAGE DESCRIPTION TEMPERATURE RANGE LT3837EFE PBF LT3837EFE TRPBF 3837EFE 16-Lead Plastic TSSOP 40C to 125C LT3837IFE PBF LT3837IFE TRPBF 3837FE 16-Lead Plastic TSSOP 40C to 125C LEAD BASED FINISH TAPE AND REEL PART MARKING PACKAGE DESCRIPTION TEMPERATURE RANGE LT3837EFE LT3837EFE TR 3837EFE 16-Lead Plastic 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: