Linear Technology Analog Devices LT8708-1, Datasheet

Page: 2 / 36

LT8708-1
2
Rev 0
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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 ................... 8
Pin Functions ..............................................10
Block Diagram .............................................13
Operation...................................................14
Common LT8708-1 and LT8708 Features ............... 14
Adding Phases to an LT8708 Application ................ 14
Adding Phases: The Master LT8708 .................... 14
Adding Phases: The Slave LT8708-1 .................... 16
Start-Up .................................................................. 17
Start-Up: SWEN Pin .............................................. 17
Start-Up: Soft-Start of Switching Regulator ......... 18
Control Overview .................................................... 18
Power Switch Control ............................................ 19
Unidirectional and Bidirectional Conduction ........... 19
Error Amplifiers ...................................................... 19
Transfer Function: I
OUT(SLAVE)
Vs I
OUT(MASTER)
......20
Transfer Function: CCM ........................................21
Transfer Function: DCM, HCM and Burst Mode
Operation ............................................................21
Current Monitoring and Limiting .............................21
Monitoring: I
OUT(SLAVE)
.........................................21
Monitoring and Limiting: I
IN(SLAVE)
......................21
Multiphase Clocking ...............................................22
Applications Information ................................23
Quick-Start Multiphase Setup .................................23
Quick Setup: Design the Master Phase .................23
Quick Setup: Design the Slave Phase(s) ...............23
Quick Setup: Evaluation ........................................23
Choosing the Total Number of Phases ....................23
Operating Frequency Selection ............................... 24
C
IN
and C
OUT
Selection ........................................... 24
C
IN
and C
OUT
Selection: V
IN
Capacitance .............. 24
C
IN
and C
OUT
Selection: V
OUT
Capacitance ...........25
VINHIMON, VOUTLOMON and RVSOFF ..................25
Configuring the I
IN(SLAVE)
Current Limits ................26
Regulating I
OUT(SLAVE)
............................................26
I
OUT(SLAVE)
: Circuit Description .............................26
I
OUT(SLAVE)
: Configuration ....................................28
Loop Compensation ................................................28
Voltage Lockouts ....................................................29
Circuit Board Layout Checklist ...............................29
Design Example .....................................................29
Typical Applications ......................................31
Package Description .....................................35
Typical Application .......................................36
Related Parts ..............................................36