Datasheet LTC7891 (Analog Devices) - 2
| Manufacturer | Analog Devices |
| Description | 100 V, Low IQ, Synchronous Step-Down Controller for GaN FETs in 28-Lead QFN (4mm x 5mm, Plastic Side Wettable) package |
| Pages / Page | 36 / 2 — LTC7891. TABLE OF CONTENTS. REVISION HISTORY. 4/2025—Rev. 0 to Rev. A. … |
| File Format / Size | PDF / 1.7 Mb |
| Document Language | English |
LTC7891. TABLE OF CONTENTS. REVISION HISTORY. 4/2025—Rev. 0 to Rev. A. 5/2022—Revision 0: Initial Version. analog.com
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LTC7891 TABLE OF CONTENTS
Features.. 1 Current Sense Selection.. 18 Applications... 1 Low Value Resistor Current Sensing..19 Typical Application Circuit ...1 Inductor DCR Current Sensing...19 General Description...1 Setting the Operating Frequency... 20 Specifications.. 3 Selecting the Light Load Operating Mode..21 Electrical Characteristics.. 3 Dead Time Control (DTCA and DTCB Pins).. 21 Absolute Maximum Ratings...6 CIN and COUT Selection..23 ESD Caution...6 Setting the Output Voltage... 23 Pin Configuration and Function Descriptions.. 7 RUN Pin and Undervoltage Lockout.. 24 Typical Performance Characteristics... 9 Soft Start and Tracking (TRACK/SS Pin)... 24 Theory of Operation...15 INTVCC Regulators (OPTI-DRIVE)...25 Functional Diagram.. 15 Topside FET Driver Supply (CB)...26 Main Control Loop..15 Minimum On Time Considerations... 26 Power and Bias Supplies (VIN, EXTVCC, Fault Conditions: Current Limit and Foldback.. 26 DRVCC, and INTVCC)..15 Fault Conditions: Overvoltage Protection...27 High-Side Bootstrap Capacitor...15 Fault Conditions: Overtemperature Dead Time Control (DTCA and DTCB Pins).. 16 Protection... 27 Startup and Shutdown (RUN and Phase-Locked Loop and Frequency TRACK/SS Pins).. 16 Synchronization..27 Light Load Operation: Burst Mode Efficiency Considerations... 27 Operation, Pulse Skipping Mode, or Checking Transient Response... 28 Forced Continuous Mode (MODE Pin)...16 Design Example... 28 Frequency Selection, Spread Spectrum, PCB Layout Checklist...29 and Phase-Locked Loop (FREQ and PCB Layout Debugging..30 PLLIN/SPREAD Pins).. 17 Typical Applications..32 Output Overvoltage Protection... 17 Related Products..35 Foldback Current..17 Outline Dimensions... 36 Power Good... 17 Ordering Guide...36 Applications Information.. 18 Evaluation Boards.. 36 Inductor Value Calculation..18 Automotive Products.. 36 Inductor Core Selection..18
REVISION HISTORY 4/2025—Rev. 0 to Rev. A
Changes to Features Section.. 1 Changes to Applications Section .. 1 Changes to Ordering Guide .. 36 Added Automotive Products Section... 36
5/2022—Revision 0: Initial Version analog.com Rev. A | 2 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
LTC7891 TABLE OF CONTENTS
Features.. 1 Current Sense Selection.. 18 Applications... 1 Low Value Resistor Current Sensing..19 Typical Application Circuit ...1 Inductor DCR Current Sensing...19 General Description...1 Setting the Operating Frequency... 20 Specifications.. 3 Selecting the Light Load Operating Mode..21 Electrical Characteristics.. 3 Dead Time Control (DTCA and DTCB Pins).. 21 Absolute Maximum Ratings...6 CIN and COUT Selection..23 ESD Caution...6 Setting the Output Voltage... 23 Pin Configuration and Function Descriptions.. 7 RUN Pin and Undervoltage Lockout.. 24 Typical Performance Characteristics... 9 Soft Start and Tracking (TRACK/SS Pin)... 24 Theory of Operation...15 INTVCC Regulators (OPTI-DRIVE)...25 Functional Diagram.. 15 Topside FET Driver Supply (CB)...26 Main Control Loop..15 Minimum On Time Considerations... 26 Power and Bias Supplies (VIN, EXTVCC, Fault Conditions: Current Limit and Foldback.. 26 DRVCC, and INTVCC)..15 Fault Conditions: Overvoltage Protection...27 High-Side Bootstrap Capacitor...15 Fault Conditions: Overtemperature Dead Time Control (DTCA and DTCB Pins).. 16 Protection... 27 Startup and Shutdown (RUN and Phase-Locked Loop and Frequency TRACK/SS Pins).. 16 Synchronization..27 Light Load Operation: Burst Mode Efficiency Considerations... 27 Operation, Pulse Skipping Mode, or Checking Transient Response... 28 Forced Continuous Mode (MODE Pin)...16 Design Example... 28 Frequency Selection, Spread Spectrum, PCB Layout Checklist...29 and Phase-Locked Loop (FREQ and PCB Layout Debugging..30 PLLIN/SPREAD Pins).. 17 Typical Applications..32 Output Overvoltage Protection... 17 Related Products..35 Foldback Current..17 Outline Dimensions... 36 Power Good... 17 Ordering Guide...36 Applications Information.. 18 Evaluation Boards.. 36 Inductor Value Calculation..18 Automotive Products.. 36 Inductor Core Selection..18
REVISION HISTORY 4/2025—Rev. 0 to Rev. A
Changes to Features Section.. 1 Changes to Applications Section .. 1 Changes to Ordering Guide .. 36 Added Automotive Products Section... 36
5/2022—Revision 0: Initial Version analog.com Rev. A | 2 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