LTC3725 Single-Switch Forward Controller and Gate Driver FEATURES DESCRIPTIO High Speed Gate Driver for Forward Converter The LTC 3725 is a controller for a single-switch forward On-Chip Rectifier and Self-Starting Architecture converter and includes an on-chip gate driver. Eliminates Need for Separate Gate Drive Bias For secondary-side control, combine the LTC3725 with Supply the LTC3706 PolyPhase secondary-side synchronous Wide Input Voltage Supply Range: 9V and Up forward controller to create a complete forward converter Linear Regulator Controller for Fast Start-Up using a minimum of discrete parts. A proprietary scheme Precision UVLO with Adjustable Hysteresis is used to multiplex gate drive signals across the isolation Overcurrent Protection barrier through a tiny pulse transformer. The on-chip Volt-Second Limit Prevents Transformer Core rectifier and the same pulse transformer provide gate drive Saturation bias power. Voltage Feedforward for Fast Transient Response Alternatively, the LTC3725 can be used as a standalone Available in 10-Lead MSOP Package voltage mode controller in a primary-side control architec- U APPLICATIO S ture with optoisolator feedback. Voltage feedforward pro- vides excellent line regulation and transient response. Isolated 48V Telecommunication Systems , LT, LTC and LTM are registered trademarks of Linear Technology Corporation. Internet Servers and Routers PolyPhase is a registered trademark of Linear Technology Corporation. All other trademarks are the property of their respective owners. Patent Pending Distributed Power Step-Down Converters Automotive and Heavy Equipment TYPICAL APPLICATIO 36V-72V to 3.3V/30A Isolated Single-Switch Forward Converter + V T1 IN 36V TO 72V L1 0.85H + V OUT 1F 3.3V 100V B0540W 30A 2 100F + 220F HAT2165 HAT2165 1.2 6.3V Si7450DP 6.3V 2 2 1/4W 2 2.2nF 0.030 200V 0.0012 1W 10F V IN 1W V OUT 2.2F FCX491A 100k FDC2512 2.74k 0.1F 1F + NDRV GATE I FG SW I I SG V NDRV V MODE S S S IN CC + + V FB/IN PT CC T2 365k 5.1k UVLO LTC3725 LTC3706 FB 1F SSFLT FS/IN PT 15k V GND PGND RUN/SS SLP REGSD FS/SYNC PHASE I TH SLMT PGND GND 162k 604 33nF 3.3k 33nF 100k 470pF L1: PULSE PA1294.910 47nF T1: PULSE PA0815 3725 TA01 T2: PULSE PA0297 3725fa 1 U ULTC3725 UUW ABSOLUTE AXI U RATI GS PACKAGE/ORDER I FOR ATIO (Note 1) TOP VIEW Power Supply (V ) ...................................0.3V to 15V CC UVLO 1 10 I S External NMOS Drive (NDRV) ....................0.3V to 20V SSFLT 2 9 V SLMT NDRV 3 11 8 V CC NDRV to V ........................................................... 0.3V to 5V + CC FB/IN 4 7 GATE FS/IN 5 6 PGND Soft-Start Fault, Feedback, MSE PACKAGE Frequency Set, Transformer 10-LEAD PLASTIC MSOP + Inputs (SSFLT, FB/IN , FS/IN ) ..................0.3V to 15V T = 125C, = 45C/W, = 10C/W JMAX JA JC EXPOSED PAD (PIN 11) IS GND, MUST BE SOLDERED TO PCB All Other Pins (V , I , UVLO) .................0.3V to 5V SLMT S Peak Output Current <1s (GATE) ............................. 2A ORDER PART NUMBER MSE PART MARKING Operating Ambient Temperature Range .. 40C to 85C Operating Junction Temperature (Note 2) ............ 125C LTC3725EMSE LTBSV Storage Temperature Range ................. 65C to 150C LTC3725IMSE LTBSW Lead Temperature (Soldering, 10 sec).................. 300C Order Options Tape and Reel: Add TR Lead Free: Add PBF Lead Free Tape and Reel: Add TRPBF Lead Free Part Marking: