LT3837 Isolated No-Opto Synchronous Flyback Controller FEATURESDESCRIPTION n Senses Output Voltage Directly from Primary Side The LT®3837 is an isolated switching regulator controller Winding—No 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 APPLICATIONS mode which improves cross regulation in multiple winding 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 CurrentTYPICAL APPLICATION 90 9V –18V to 3.3V at 10A Isolated Converter 9VIN 18VIN 88 VIN 86 22.1k 84 10µF BAS16 100nH 82 OUTPUT 3.3V/10A 2N3906 EFFICIENCY (%) 80 22µF • V 86.6k 2.2nF 47µF × 3 220µF CC • 78 FB 10Ω UVLO B0540W V 76 C 3k 2 3 4 5 6 7 8 9 10 1nF 15k 10Ω 47pF LT3837 LOAD CURRENT (A) 3837 TA01b 20k OSC FMMT618 1µF Regulation vs Load Current 3.3nF Si7336ADP SFST 3.60 100k PG Si7852DP FMMT718 tON 150k SENSE+ ENDLY 3.50 12k 8mΩ PGDLY 1.37k SENSE– 3.40 RCMP 0.1µF 2.2nF 0.1µF 330Ω 15Ω 9VIN SG 3.30 CCMP • • 18VIN GND 10k BAT54 OUTPUT (V) 3.20 3837 TA01a 3.10 3.00 2 3 4 5 6 7 8 9 10 LOAD CURRENT (A) 3837 TA01c 3837fd 1 Document Outline features applications description Typical Application absolute maximum ratings Pin Configuration order information electrical characteristics typical performance characteristics pin functions block diagram flyback feedback amplifier timing diagram operation applications information typical application Package description Revision History related parts
