LT3752/LT3752-1 TABLE OF CONTENTS Features ... 1 FORWARD CONTROLLER ...27 Applications .. 1 Adaptive Leading Edge Blanking Plus Typical Application .. 1 Programmable Extended Blanking..27 Description.. 1 Current Sensing and Programmable Slope Table of Contents .. 2 Compensation ..28 Absolute Maximum Ratings .. 3 Overcurrent: Hiccup Mode ..28 Order Information .. 3 Programming Maximum Duty Cycle Clamp: DVSEC Pin Configuration .. 3 (Volt-Second Clamp) ..29 Electrical Characteristics ... 4 DVSEC Open Loop Control: No Opto-Coupler, Error Pin Functions ..13 Amplifier or Reference ..30 Block Diagram ...15 RIVSEC: Open Pin Detection Provides Safety ...30 Timing Diagrams ...16 Transformer Reset: Active Clamp Technique ...30 Operation...19 LO Side Active Clamp Topology (LT3752) ...32 Introduction ... 19 HI Side Active Clamp Topology (LT3752-1) ...33 LT3752 Part Start-Up ... 19 Active Clamp Capacitor Value and LT3752-1 Part Start-Up .. 19 Voltage Ripple ..33 Applications Information ..21 Active Clamp MOSFET Selection ..34 Programming System Input Undervoltage Lockout Programming Active Clamp Switch Timing: AOUT (UVLO) Threshold and Hysteresis ..21 to OUT (tAO) and OUT to AOUT (tOA) Delays ...35 Soft-Stop Shutdown ...21 Programming Synchronous Rectifier Timing: Micropower Shutdown ...21 SOUT to OUT (tSO) and OUT to SOUT (tOS) Programming System Input Overvoltage Lockout Delays ...35 (OVLO) Threshold ...21 Soft-Start (SS1, SS2) ...36 LT3752-1 Micropower Start-Up from High System Soft-Stop (SS1) ..36 Input Voltages ..22 Hard-Stop (SS1, SS2) ...37 Programming Switching Frequency ..23 OUT, AOUT, SOUT Pulse-Skipping Mode ..37 Synchronizing to an External Clock ..23 AOUT Timeout ..38 INTVCC Regulator Bypassing and Operation ..24 Main Transformer Selection ...38 HOUSEKEEPING CONTROLLER .. 24 Primary-Side Power MOSFET Selection ...40 Housekeeping: Operation ..25 Synchronous Control (SOUT) ...40 Housekeeping: Soft-Start/Shutdown ..25 Output Inductor Value ... 41 Housekeeping: Programming Output Voltage ...25 Output Capacitor Selection ... 41 Housekeeping: Programming Cycle-by-Cycle Peak Input Capacitor Selection ... 41 Inductor Current and Slope Compensation ...25 PCB Layout / Thermal Guidelines ..42 Housekeeping: Adaptive Leading Edge Blanking .26 Typical Applications ..44 Housekeeping: Overcurrent Hiccup Mode ...26 Package Description ...50 Housekeeping: Output Overvoltage and Power Revision History ..51 Good ..26 Typical Application ...52 Housekeeping: Transformer Turns Ratio and Related Parts ..52 Leakage Inductance ..26 Housekeeping: Operating Without This Supply ...27 Rev. C 2 For more information www.analog.com Document Outline Features Applications Typical Application Description Table of Contents Absolute Maximum Ratings Order Information Pin Configuration Order Information Electrical Characteristics Pin Functions Block Diagram Timing Diagrams Operation Applications Information Typical Applications Package Description Revision History Typical Application Related Parts