Table Of Contents - Linear Technology Analog Devices LT8708 Datasheet

LT8708

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
Typical Performance Characteristics .................. 11
Pin Functions .............................................. 13
Block Diagram ............................................. 15
Operation................................................... 16
Typographical Conventions ..................................... 16
Start-Up .................................................................. 16
Start-Up: SHDN Pin ............................................ 16
Start-Up: SWEN Pin ............................................ 16
Start-Up: Soft-Start of Switching Regulator ....... 17
Control Overview .................................................... 17
Power Switch Control ............................................ 18
Switch Control: Buck Region (V
Switch Control: Buck-Boost (V
Switch Control: Boost Region (V
Switch Control: Soft-Start ..................................20
Uni and Bidirectional Conduction ............................20
Bidirectional Conduction: CCM .......................... 21
Unidirectional Conduction: DCM ......................... 21
Unidirectional Conduction: HCM .........................22
Unidirectional Conduction: Burst Mode ..............22
Error Amplifiers ......................................................22
V Regulation and Sensing .................................23
OUT
V : Regulation .................................................23
OUT
V : Above Regulation ......................................23
OUT
V : Below Regulation and Undervoltage .........23
OUT
V Regulation and Sensing .................................... 24
IN
V : Regulation ................................................... 24
IN
V : Above Regulation and Overvoltage .............. 24
IN
V : Below Regulation ......................................... 24
IN
Current Monitoring and Limiting ............................. 24
Monitoring and Limiting: IMON Pins .................. 24
Monitoring: ICP and ICN Pins .............................25
INTV /EXTV /GATEV
CC CC
CLKOUT and Temperature Sensing .........................25
2
>> V ) ....... 19
IN OUT
≅
V ) ......... 19
IN OUT
<< V ) ......20
IN OUT
/LDO33 Power ...............25
CC
For more information
Applications Information ................................ 26
Verify the Power Flow Conditions ...........................26
Operating Frequency Selection ...............................26
Internal Oscillator ................................................... 27
SYNC Pin and Clock Synchronization ..................... 27
CLKOUT Pin and Clock Synchronization ................. 27
Inductor Current Sensing and Slope Compensation .... 27
R Selection and Maximum Current ................ 28
SENSE
R Selection: Max R
SENSE
Boost Region ...................................................... 28
R Selection: Max R
SENSE
Buck Region .......................................................30
R Selection: Final R
SENSE
R Filtering ...................................................... 32
SENSE
Inductor (L) Selection ............................................ 32
L Selection: Load Current in Buck and
Boost Regions .................................................... 32
L Selection: Subharmonic Oscillations ...............33
L Selection: Maximum Current Rating ................33
Power MOSFET Selection .......................................34
C and C Selection ........................................... 37
IN OUT
Schottky Diode (D1, D2, D3, D4) Selection .............38
Topside MOSFET Driver Supply (C
Top Driver: Boost Cap Charge Control Block ......39
Top Driver: Boost Diodes D
VINHIMON, VOUTLOMON and RVSOFF ..................39
I and I Current Monitoring and Limiting ......... 42
IN OUT
Loop Compensation ................................................44
INTV Regulators and EXTV
CC
LDO33 Regulator ....................................................45
Voltage Lockouts ....................................................46
Junction Temperature Measurement ......................46
Thermal Shutdown ................................................. 47
Efficiency Considerations ...................................... 47
Circuit Board Layout Checklist ............................... 47
Hot Plugging Considerations ................................. 49
Design Example ...................................................... 49
Typical Applications ...................................... 55
Package Description ..................................... 63
Typical Application ....................................... 64
Related Parts .............................................. 64
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in the
SENSE
in the
SENSE
Value ................. 31
SENSE
, D , C , D ) ... 39
B1 B1 B2 B2
and D 39
B1 B2 ...................
Connection ...........45
CC
Rev 0