LT3752_15 datasheet(2/52 Pages) LINER

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LT3752/LT3752-1

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TABLE OF CONTENTS

Features..................................................... 1

Applications ................................................ 1

Typical Application ........................................ 1

Description.................................................. 1

Table of Contents .......................................... 2

Absolute Maximum Ratings.............................. 3

Order Information.......................................... 3

Pin Configuration .......................................... 3

Electrical Characteristics................................. 4

Pin Functions ..............................................13

Block Diagram.............................................15

Timing Diagrams .........................................16

Operation...................................................19

Introduction ....................................................... 19

LT3752 Part Start-Up ......................................... 19

LT3752-1 Part Start-Up ...................................... 19

Applications Information ................................21

Programming System Input Undervoltage Lockout

(UVLO) Threshold and Hysteresis ......................21

Soft-Stop Shutdown...........................................21

Micropower Shutdown .......................................21

Programming System Input Overvoltage Lockout

(OVLO) Threshold...............................................21

LT3752-1 Micropower Start-Up from High System

Input Voltages ....................................................22

Programming Switching Frequency....................23

Synchronizing to an External Clock ....................23

INTVCC Regulator Bypassing and Operation ......24

HOUSEKEEPING CONTROLLER.............................. 24

Housekeeping: Operation....................................25

Housekeeping: Soft-Start/Shutdown ..................25

Housekeeping: Programming Output Voltage.....25

Housekeeping: Programming Cycle-by-Cycle Peak

Inductor Current and Slope Compensation.........25

Housekeeping: Adaptive Leading Edge Blanking.26

Housekeeping: Overcurrent Hiccup Mode...........26

Housekeeping: Output Overvoltage and Power

Good ..................................................................26

Housekeeping: Transformer Turns Ratio and

Leakage Inductance............................................26

Housekeeping: Operating Without This Supply...27

FORWARD CONTROLLER.......................................27

Adaptive Leading Edge Blanking Plus

Programmable Extended Blanking......................27

Current Sensing and Programmable Slope

Compensation ....................................................28

Overcurrent: Hiccup Mode..................................28

Programming Maximum Duty Cycle Clamp: DVSEC

(Volt-Second Clamp) ..........................................29

DVSEC Open Loop Control: No Opto-Coupler, Error

Amplifier or Reference........................................30

RIVSEC: Open Pin Detection Provides Safety.......30

Transformer Reset: Active Clamp Technique .....30

LO Side Active Clamp Topology (LT3752)...........32

HI Side Active Clamp Topology (LT3752-1).........33

Active Clamp Capacitor Value and

Voltage Ripple ....................................................33

Active Clamp MOSFET Selection ........................34

Programming Active Clamp Switch Timing: AOUT

to OUT (tAO) and OUT to AOUT (tOA) Delays.......35

Programming Synchronous Rectifier Timing:

SOUT to OUT (tSO) and OUT to SOUT (tOS)

Delays.................................................................35

Soft-Start (SS1, SS2) .........................................36

Soft-Stop (SS1) ..................................................36

Hard-Stop (SS1, SS2).........................................37

OUT, AOUT, SOUT Pulse-Skipping Mode............37

AOUT Timeout ....................................................38

Main Transformer Selection ...............................38

Primary-Side Power MOSFET Selection .............40

Synchronous Control (SOUT).............................40

Output Inductor Value......................................... 41

Output Capacitor Selection................................. 41

Input Capacitor Selection ................................... 41

PCB Layout / Thermal Guidelines ......................42

Typical Applications ......................................44

Package Description .....................................50

Revision History ..........................................51

Typical Application .......................................52

Related Parts ..............................................52

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