LT8228 datasheet(2/69 Pages) AD

2 / 69 page

LT8228

Rev. A

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TABLE OF CONTENTS

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

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

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

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

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

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

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

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

Typical Performance Characteristics ................... 9

Buck Efficiency and Operation ..................................9

Typical Performance Characteristics ..................11

Boost Efficiency and Operation............................... 11

ENABLE, Supply Current and VCC...................................13

SS Current, Frequency, Thresholds and Driver ...... 15

Protection MOSFET Controller................................ 15

Pin Functions ..............................................16

Block Diagram.............................................23

Operation...................................................24

Overview................................................................. 24

Buck Mode Operation ............................................. 24

Boost Mode Operation............................................25

V1 Protection MOSFET Controller Operation ..........26

V2 Protection MOSFET Controller Operation ..........28

Mode of Operation (DRXN).....................................28

Enable and Soft-Start (Enable and SS) ...................29

Paralleling Multiple Controllers (ISHARE

and IGND)...............................................................30

BIAS Supply and VCC Regulators............................31

Strong Gate Drivers ................................................32

Frequency Selection, Spread Spectrum and Phase-

Locked Loop (RT and SYNC) ..................................32

FAULT Monitoring and REPORT Feature..................32

Applications Information ................................33

Introduction............................................................33

Programming the Switching Frequency..................33

Inductor Selection...................................................34

RSNS2 and RIN2 Selection for Peak Inductor

Current....................................................................35

RSET2P Selection for V2 Output Current

Limit (Buck Mode) .................................................36

RSET2N Selection for V2 Input Current

Limit (Boost Mode) ................................................37

RMON2 Selection for V2 Current Monitoring............38

RSNS1 and RIN1 Selection........................................38

RSET1P Selection for V1 Input Current

Limit (Buck Mode) .................................................39

RSET1N Selection for V1 Output Current

Limit (Boost Mode) ................................................40

RMON1 Selection for V1 Current Monitoring............41

Output Voltage, Input Undervoltage and Output

Overvoltage Programming...................................... 41

Power MOSFET Selection and Efficiency

Considerations........................................................42

Optional Schottky Diode (D2 and D3) Selection .....45

Top MOSFET Driver Supply (CBST, DBST)................46

Power Path Capacitor Selection..............................46

Loop Compensation................................................48

Inrush Current Control............................................49

Boost Output Short Protection and Timer...............50

FAULT Conditions....................................................52

Soft-Start................................................................53

REPORT Feature......................................................53

Paralleling Multiple LT8228s...................................56

BIAS, DRVCC, INTVCC and Power Dissipation .........57

Thermal Shutdown .................................................58

Pin Clearance/Creepage Consideration ...................59

Efficiency Considerations .......................................59

PC Board Layout Checklist .....................................59

Design Example......................................................60

Package Description .....................................67

Revision History ..........................................68

Typical Application .......................................69

Related Parts ..............................................69

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