LT3753_15 datasheet(2/36 Pages) LINER

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LT3753

3753f

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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

Typical Performance Characteristics ................... 7

Pin Functions ..............................................10

Block Diagram.............................................11

Timing Diagrams .........................................12

Operation...................................................14

Introduction ....................................................... 14

Part Start-Up...................................................... 14

Applications Information ................................15

Programming System Input Undervoltage

Lockout (UVLO) Threshold and Hysteresis......... 15

Soft-Stop Shutdown........................................... 15

Micropower Shutdown ....................................... 15

Programming System Input Overvoltage

Lockout (OVLO) Threshold ................................. 15

Programming Switching Frequency.................... 16

Synchronizing to an External Clock .................... 16

INTVCC Regulator Bypassing and Operation ...... 16

Adaptive Leading Edge Blanking Plus

Programmable Extended Blanking...................... 17

Current Sensing and Programmable Slope

Compensation .................................................... 18

Overcurrent: Hiccup Mode.................................. 18

Programming Maximum Duty Cycle Clamp:

DVSEC (Volt-Second Clamp)................................ 18

DVSEC Open Loop Control: No Opto-Coupler,

Error Amplifier or Reference............................... 19

RIVSEC: Open Pin Detection Provides Safety....... 19

Transformer Reset: Active Clamp Technique .....20

LO Side Active Clamp Topology (LT3753)...........20

HI Side Active Clamp Topology (LT3752-1).........22

Active Clamp Capacitor Value and Voltage

Ripple .................................................................22

Active Clamp MOSFET Selection ........................23

Programming Active Clamp Switch Timing:

AOUT to OUT (tAO) and OUT to AOUT (tOA)

Delays................................................................. 24

Programming Synchronous Rectifier Timing:

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

Delays................................................................. 24

Soft-Start (SS1, SS2) .........................................25

Soft-Stop (SS1) ..................................................25

Hard-Stop (SS1, SS2).........................................26

OUT, AOUT, SOUT Pulse-Skipping Mode............27

AOUT Timeout ....................................................27

Main Transformer Selection ...............................27

Generating Auxiliary Supplies.............................28

Primary-Side Auxiliary Supply............................29

Secondary-Side Auxiliary Supply .......................29

Primary-Side Power MOSFET Selection .............30

Synchronous Control (SOUT).............................31

Output Inductor Value.........................................32

Output Capacitor Selection.................................32

Input Capacitor Selection ...................................32

PCB Layout / Thermal Guidelines ......................33

Package Description .....................................35

Typical Application .......................................36

Related Parts ..............................................36

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