Datasheet LTC7892 (Analog Devices) - 2

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Data Sheet LTC7892 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 .. 10 Typical Performance Characteristics ... 14 Functional Diagram ... 19 Theory of Operation .. 20 Main Control Loop ... 20 Power and Bias Supplies (VBIAS, EXTVCC, DRVCC, INTVCC) .. 20 High Side Bootstrap Capacitor ... 20 Dead Time Control (DTCA and DTCB Pins) .. 21 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 Output Overvoltage Protection .. 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 Pin Tied to Ground (Adaptive Dead Time Control) .. 31 DTCx Pin connected with a resistor to GND .. 31 Power FET Selection ... 32 CIN and COUT Selection .. 33 Single Output 2-Phase Operation .. 34
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Rev. 0 2 of 50 Document Outline Features Applications General Description Typical Application Revision History Specifications Absolute Maximum Ratings Pin Configurations and Function Descriptions Typical Performance Characteristics Functional Diagram Theory of Operation Main Control Loop Power and Bias Supplies (VBIAS, EXTVCC, DRVCC, INTVCC) High Side Bootstrap Capacitor Dead Time Control (DTCA and DTCB Pins) Start-Up and Shutdown (RUN and SS Pins) Light Load Operation: Burst Mode Operation, Pulse-Skipping Mode, or Forced Continuous Mode (MODE Pin) Frequency Selection, Spread Spectrum, and Phase-Locked Loop (FREQ and PLLIN/SPREAD Pins) Output Overvoltage Protection Power Good Applications Information Inductor Value Calculation Inductor Core Selection Current Sense Selection Low Value Resistor Current Sensing Inductor DCR Current Sensing Setting the Operating Frequency Selecting the Light-Load Operating Mode Dead Time Control (DTCA and DTCB Pins) DTCx Pin Tied to Ground (Adaptive Dead Time Control) DTCx Pin connected with a resistor to GND Power FET Selection CIN and COUT Selection Single Output 2-Phase Operation Setting the Output Voltage RUNx Pins and Undervoltage Lockout Soft Start (SSx Pins) INTVCC Regulators (OPTI-DRIVE) Topside FET Driver Supply (CB) Minimum On-Time Considerations Fault Conditions: Overtemperature Protection Phase-Locked Loop and Frequency Synchronization Efficiency Considerations Checking Transient Response Design Example PCB Board Layout Checklist PCB Layout Debugging Typical Applications Related Parts Outline Dimensions Ordering Guide