Data Sheet LTC7891TYPICAL PERFORMANCE CHARACTERISTICSFigure 7. Load Step Burst Mode OperationFigure 4. Efficiency and Power Loss vs. Load CurrentFigure 8. Load Step Pulse Skipping ModeFigure 5. Efficiency vs. Load CurrentFigure 9. Load Step Forced Continuous ModeFigure 6. Efficiency vs. Input Voltage (ILOAD Is Load Current)analog.comRev. A | 9 of 36 Document Outline Features Applications Typical Application Circuit General Description Specifications Electrical Characteristics Absolute Maximum Ratings ESD Caution Pin Configuration and Function Descriptions Typical Performance Characteristics Theory of Operation Functional Diagram Main Control Loop Power and Bias Supplies (VIN, EXTVCC, DRVCC, and INTVCC) High-Side Bootstrap Capacitor Dead Time Control (DTCA and DTCB Pins) Startup and Shutdown (RUN and TRACK/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 Foldback Current 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 Pins Tied to GND (Adaptive Dead Time Control) DTCx Pins Tied to INTVCC (Smart Near Zero Dead Time Control) DTCx Pins Connected with a Resistor to GND Power FET Selection CIN and COUT Selection Setting the Output Voltage RUN Pin and Undervoltage Lockout Soft Start and Tracking (TRACK/SS Pin) INTVCC Regulators (OPTI-DRIVE) Topside FET Driver Supply (CB) Minimum On Time Considerations Fault Conditions: Current Limit and Foldback Fault Conditions: Overvoltage Protection Fault Conditions: Overtemperature Protection Phase-Locked Loop and Frequency Synchronization Efficiency Considerations Checking Transient Response Design Example PCB Layout Checklist PCB Layout Debugging Typical Applications Related Products Outline Dimensions Ordering Guide Evaluation Boards Automotive Products