Datasheet LTC7893 (Analog Devices) - 2

link to page 1 link to page 1 link to page 1 link to page 1 link to page 3 link to page 4 link to page 8 link to page 9 link to page 12 link to page 17 link to page 17 link to page 17 link to page 18 link to page 18 link to page 18 link to page 18 link to page 19 link to page 20 link to page 20 link to page 20 link to page 21 link to page 21 link to page 21 link to page 22 link to page 22 link to page 23 link to page 25 link to page 26 link to page 27 link to page 27 link to page 28 link to page 29 link to page 29 link to page 30
Data Sheet LTC7893 TABLE OF CONTENTS
Features .. 1 Applications ... 1 General Description ... 1 Typical Application .. 1 Revision History ... 3 Specifications ... 4 Absolute Maximum Ratings .. 8 Pin Configurations and Function Descriptions .. 9 Typical Performance Characteristics ... 12 Functional diagram ... 17 Theory of Operation .. 17 Main Control Loop ... 17 Power and Bias Supplies (VBIAS, EXTVCC, DRVCC, and INTVCC) .. 18 High-Side Bootstrap Capacitor .. 18 Dead Time Control (DTCA and DTCB Pins) .. 18 Startup and Shutdown (RUN and SS Pins) .. 18 Light Load Operation: Burst Mode Operation, Pulse-Skipping, or Forced Continuous Mode (MODE Pin) ... 19 Frequency Selection, Spread Spectrum, and Phase-Locked Loop (FREQ and PLLIN/SPREAD Pins) .. 20 Output Overvoltage Protection .. 20 Power Good ... 20 Applications Information .. 21 Inductor Value Calculation ... 21 Inductor Core Selection .. 21 Current Sense Selection ... 22 Low Value Resistor Current Sensing .. 22 Inductor DCR Current Sensing ... 23 Setting the Operating Frequency ... 25 Selecting the Light-Load Operating Mode ... 26 Dead Time Control (DTCA and DTCB Pins) .. 27 DTCx Pin Tied to Ground (Adaptive Dead Time Control) .. 27 DTCx Pin connected with a resistor to GND .. 28 Power FET Selection ... 29 CIN and COUT Selection .. 29 Setting the Output Voltage ... 30
analog.com
Rev. 0 2 of 48 Document Outline Features Applications General Description Typical Application TABLE OF CONTENTS 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, and INTVCC) High-Side Bootstrap Capacitor Dead Time Control (DTCA and DTCB Pins) Startup and Shutdown (RUN and SS Pins) Light Load 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) 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 Setting the Output Voltage RUN Pin and Undervoltage Lockout Soft-Start (SS Pin) 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