LT1725IGN#TRPBF Analog Devices

LT1725 General Purpose Isolated Flyback Controller FEATURES DESCRIPTIO Drives External Power MOSFET with External The LT 1725 is a monolithic switching regulator control- I Resistor ler specifically designed for the isolated flyback topology. SENSE Application Input Voltage Limited Only by It drives the gate of an external MOSFET and is generally External Power Components powered from a third transformer winding. These features Senses Output Voltage Directly from Primary Side allow for an application input voltage limited only by WindingNo Optoisolator Required external power path components. The third transformer Accurate Regulation Without User Trims winding also provides output voltage feedback informa- Regulation Maintained Well into Discontinuous Mode tion, such that an optoisolator is not required. Its gate Switching Frequency from 50kHz to 250kHz with drive capability coupled with a suitable external MOSFET External Capacitor can deliver load power up to tens of watts. Optional Load Compensation The LT1725 has a number of features not found on most Optional Undervoltage Lockout other switching regulator ICs. By utilizing current mode Available in 16-Pin SO and SSOP Packages switching techniques, it provides excellent AC and DC line regulation. Its unique control circuitry can maintain regu- U lation well into discontinuous mode in most applications. APPLICATIO S Optional load compensation circuitry allows for improved Telecom Isolated Converters load regulation. An optional undervoltage lockout pin Offline Isolated Power Supplies halts operation when the application input voltage is too Instrumentation Power Supplies low. An optional external capacitor implements a soft- start function. A 3V output is available at up to several mA , LTC and LT are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. for powering primary side application circuitry. TYPICAL APPLICATIO 48V to Isolated 5V Converter CTX02-14989 Output Load Regulation 6 470pF 5.25 LT1725 18 V 36V TO 72V 35.7k IN BAS16 3V OUT 1 1% V = 48V IN V = 36V FB IN 22 47k 3.01k V = 5V OUT V SFST CC V = 72V IN 1% I = 0 to 2A 1nF 2 OUT + 9 12CWQ06 15F 1F 5.00 VC 51 68 47pF 1W OSCAP 11 150pF 820k t UVLO ON 10 + 51k 100pF 33k 1.5F 150F ENDLY 51k 4.75 4 12 MENAB 0 0.5 1.0 1.5 2.0 51k I (A) LOAD R GATE IRF620 OCMP 1725 F10b 2.7k I R CMPC SENSE 0.1F SGND PGND 0.18 1725 TA01a 1725fa 1 V (V) OUT U ULT1725 UUW ABSOLUTE AXI U RATI GS PACKAGE/ORDER I FOR ATIO (Note 1) TOP VIEW V Supply Voltage................................................. 22V CC PGND 1 16 GATE UVLO Pin Voltage .................................................... V CC I 2 15 V I Pin Voltage .................................................... 2V SENSE CC SENSE SFST 3 14 t ON FB Pin Current ..................................................... 2mA R 4 13 ENDLY OCMP Operating Junction R 5 12 MINENAB CMPC Temperature Range OSCAP 6 11 SGND LT1725C .............................................. 0C to 100C V 7 10 UVLO C LT1725I ........................................... 40C TO 125C FB 8 9 3V OUT Storage Temperature Range ................ 65C to 150C GN PACKAGE S PACKAGE Lead Temperature (Soldering, 10 sec)................ 300C 16-LEAD PLASTIC SSOP 16-LEAD PLASTIC SO T = 125C, = 110C/W (GN) JMAX JA T = 125C, = 100C/W (SO) JMAX JA GN PART MARKING ORDER PART NUMBER LT1725CGN 1725 LT1725IGN 1725I LT1725CS LT1725IS Order Options Tape and Reel: Add TR Lead Free: Add PBF Lead Free Tape and Reel: Add TRPBF Lead Free Part Marking: