Datasheet LTC7804 (Analog Devices) - 2

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TABLE OF CONTENTS Features ... 1 Applications Information ..15 Applications .. 1
SENSE+ and SENSE– Pins ...15
Typical Application .. 1
Low Value Resistor Current Sensing...16
Description.. 1
Inductor DCR Sensing ..16
Absolute Maximum Ratings .. 3
Inductor Value Calculation ..17
Pin Configuration .. 3
Inductor Core Selection ..17
Order Information .. 4
Power MOSFET Selection ...18
Electrical Characteristics ... 5
CIN and COUT Selection ...18
Typical Performance Characteristics ... 7
Setting Output Voltage ..19
Pin Functions ..10
RUN Pin ..19
Block Diagram ...11
Soft-Start (SS Pin) ..20
Operation...12
INTVCC Regulators ..20 Main Control Loop ..12 Topside MOSFET Driver Supply (CB, DB) ..21 INTVCC/EXTVCC Power ..12 Phase-Locked Loop and Frequency Boost Supply and Dropout (BOOST and SW Pins) ..12 Synchronization .. 21 Shutdown and Start-Up (RUN, SS Pins) ..12 Setting the Operating Frequency ...22 Light Load Current Operation: Burst Mode Selecting the Light-Load Operating Mode ...23 Operation, Pulse-Skipping or Forced Continuous Minimum On-Time Considerations ...23 Mode (MODE Pin) ...12 Fault Conditions: Overtemperature Protection ..24 Frequency Selection, Spread Spectrum and Phase- Efficiency Considerations ..24 Locked-Loop (FREQ and PLLIN/SPREAD Pins) ..13 Checking Transient Response ...24 Operation When VIN > VOUT ..14 Design Example ..25 Operation at Low Input Voltage...14 PC Board Layout Checklist ..26 BOOST Supply Refresh and Internal Charge Pump .14 PC Board Layout Debugging ...27
Typical Applications ..28 Package Description ...32 Typical Application ...34 Related Parts ..34
Rev. 0 2 For more information www.analog.com Document Outline Features Applications Typical Application Description Absolute Maximum Ratings Pin Configuration Order Information Electrical Characteristics Typical Performance Characteristics Pin Functions Block Diagram Operation Main Control Loop INTVCC/EXTVCC Power Boost Supply and Dropout (BOOST and SW Pins) Shutdown and Start-Up (RUN, SS Pins) Light Load Current Operation: Burst Mode Operation, Pulse-Skipping or Forced Continuous Mode (MODE Pin) Frequency Selection, Spread Spectrum and Phase-Locked-Loop (FREQ and PLLIN/SPREAD Pins) Operation When VIN > VOUT Operation at Low Input Voltage BOOST Supply Refresh and Internal Charge Pump Applications Information SENSE+ and SENSE– Pins Low Value Resistor Current Sensing Inductor DCR Sensing Inductor Value Calculation Inductor Core Selection Power MOSFET Selection CIN and COUT Selection Setting Output Voltage RUN Pin Soft-Start (SS Pin) INTVCC Regulators Topside MOSFET Driver Supply (CB, DB) Phase-Locked Loop and Frequency Synchronization Setting the Operating Frequency Selecting the Light-Load Operating Mode Minimum On-Time Considerations Fault Conditions: Overtemperature Protection Efficiency Considerations Checking Transient Response Design Example PC Board Layout Checklist PC Board Layout Debugging Package Description Typical Application Related Parts