Data Sheet

LTC7899

analog.com

Rev. 0

2 of 50

TABLE OF CONTENTS

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

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

General Description...................................................................................................................................................................................1

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

Revision History .........................................................................................................................................................................................3

Specifications.............................................................................................................................................................................................4

Absolute Maximum Ratings ......................................................................................................................................................................9

Pin Configurations and Function Descriptions......................................................................................................................................11

Block Diagram..........................................................................................................................................................................................14

Typical Performance Characteristics .....................................................................................................................................................15

Theory of Operation ................................................................................................................................................................................20

Main Control Loop...............................................................................................................................................................................20

Power and Bias Supplies (VBIAS, EXTVCC, DRVCC, and INTVCC) ..............................................................................................................20

High-Side Bootstrap Capacitor ..........................................................................................................................................................20

Dead Time Control (DTCA and DTCB Pins) ........................................................................................................................................20

Start-Up and Shutdown (RUN and SS Pins) ......................................................................................................................................21

Light Load Operation: Burst Mode Operation, Pulse-Skipping Mode, or Forced Continuous Mode (MODE Pin).........................21

Frequency Selection, Spread Spectrum, and Phase-Locked Loop (FREQ and PLLIN/SPREAD Pins)............................................22

PolyPhase Applications (CLKOUT and PHASMD Pins)......................................................................................................................23

Output Overvoltage Protection..........................................................................................................................................................23

Operation at Low Input Voltage.........................................................................................................................................................23

BOOST Supply Refresh .......................................................................................................................................................................23

Power Good .........................................................................................................................................................................................23

Applications Information ........................................................................................................................................................................24

Inductor Value Calculation.................................................................................................................................................................24

Inductor Core Selection......................................................................................................................................................................24

Current Sense Selection .....................................................................................................................................................................25

Low Value Resistor Current Sensing ..................................................................................................................................................25

Inductor DCR Current Sensing ...........................................................................................................................................................26

Setting the Operating Frequency ..................................................................................................................................................28

Selecting the Light Load Operating Mode ....................................................................................................................................29

Dead Time Control (DTCA and DTCB Pins)....................................................................................................................................30

DTCx Pins Tied to INTVCC or VIN- (Adaptive Dead Time Control) ...................................................................................................30

DTCx pin connected with a resistor to VIN-:....................................................................................................................................31