Datasheet LTC7891 (Analog Devices)
| Hersteller | Analog Devices |
| Beschreibung | 100 V, Low IQ, Synchronous Step-Down Controller for GaN FETs in 28-Lead QFN (4mm x 5mm, Plastic Side Wettable) package |
| Seiten / Seite | 36 / 1 — LTC7891. FEATURES. TYPICAL APPLICATION CIRCUIT. Figure 1. Typical … |
| Dateiformat / Größe | PDF / 1.7 Mb |
| Dokumentensprache | Englisch |
LTC7891. FEATURES. TYPICAL APPLICATION CIRCUIT. Figure 1. Typical Application Circuit. APPLICATIONS. GENERAL DESCRIPTION
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LTC7891
100 V, Low IQ, Synchronous Step-Down Controller for GaN FETs
FEATURES TYPICAL APPLICATION CIRCUIT
► GaN drive technology fully optimized for GaN FETs ► Wide VIN range: 4 V to 100 V ► Wide output voltage range: 0.8 V ≤ VOUT ≤ 60 V ► No catch, clamp, or bootstrap diodes needed ► Internal smart bootstrap switches prevent overcharging of high- side driver supplies ► Internally optimized, smart near zero dead times or resistor adjustable dead times ► Split output gate drivers for adjustable turn on and turn off driver strengths ► Accurate adjustable driver voltage and UVLO ► Low operating IQ: 5 μA (48 VIN to 5 VOUT) ► Programmable frequency (100 kHz to 3 MHz) ► Phase lockable frequency (100 kHz to 3 MHz)
Figure 1. Typical Application Circuit
► Spread spectrum frequency modulation ► 28-lead (4 mm × 5 mm) side wettable QFN package ► AEC-Q100 qualified for automotive applications
APPLICATIONS
► Automotive and industrial power systems ► Military avionics and medical systems ► Telecommunications power systems
GENERAL DESCRIPTION
The LTC7891 is a high performance, step-down, dc-to-dc switching regulator controller that drives all N-channel synchronous gallium nitride (GaN) field effect transistor (FET) power stages from input voltages up to 100 V. The LTC7891 solves many of the challenges traditionally faced when using GaN FETs. The LTC7891 simplifies the application design while requiring no protection diodes and no other additional external components compared to a silicon metal- oxide semiconductor field effect transistor (MOSFET) solution. The internal smart bootstrap switch prevents overcharging of the BOOST pin to SW pin high-side driver supplies during dead times, protecting the gate of the top GaN FET. The LTC7891 internally optimizes the gate driver timing on both switching edges to achieve smart near zero dead times, significantly improving efficiency and allowing for high frequency operation, even at high input voltages.
Figure 2. Efficiency and Power Loss vs. Load Current
Alternatively, the user can adjust the dead times with external resistors for margin or to tailor the application. Note that throughout this data sheet, multifunction pins, such as PLLIN/SPREAD, are referred to either by the entire pin name or The gate drive voltage of the LTC7891 can be precisely adjusted by a single function of the pin, for example, PLLIN, when only that from 4 V to 5.5 V to optimize performance, and to allow the use of function is relevant. different GaN FETs, or even logic level MOSFETs.
Rev. A DOCUMENT FEEDBACK
Information furnished by Analog Devices is believed to be accurate and reliable "as is". However, no responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other rights of third parties that may result from its use. Specifications subject to change without notice. No license is granted by implication or otherwise under any patent or patent rights of Analog Devices. Trademarks and registered
TECHNICAL SUPPORT
trademarks are the property of their respective owners. All Analog Devices products contained herein are subject to release and availability. 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
100 V, Low IQ, Synchronous Step-Down Controller for GaN FETs
FEATURES TYPICAL APPLICATION CIRCUIT
► GaN drive technology fully optimized for GaN FETs ► Wide VIN range: 4 V to 100 V ► Wide output voltage range: 0.8 V ≤ VOUT ≤ 60 V ► No catch, clamp, or bootstrap diodes needed ► Internal smart bootstrap switches prevent overcharging of high- side driver supplies ► Internally optimized, smart near zero dead times or resistor adjustable dead times ► Split output gate drivers for adjustable turn on and turn off driver strengths ► Accurate adjustable driver voltage and UVLO ► Low operating IQ: 5 μA (48 VIN to 5 VOUT) ► Programmable frequency (100 kHz to 3 MHz) ► Phase lockable frequency (100 kHz to 3 MHz)
Figure 1. Typical Application Circuit
► Spread spectrum frequency modulation ► 28-lead (4 mm × 5 mm) side wettable QFN package ► AEC-Q100 qualified for automotive applications
APPLICATIONS
► Automotive and industrial power systems ► Military avionics and medical systems ► Telecommunications power systems
GENERAL DESCRIPTION
The LTC7891 is a high performance, step-down, dc-to-dc switching regulator controller that drives all N-channel synchronous gallium nitride (GaN) field effect transistor (FET) power stages from input voltages up to 100 V. The LTC7891 solves many of the challenges traditionally faced when using GaN FETs. The LTC7891 simplifies the application design while requiring no protection diodes and no other additional external components compared to a silicon metal- oxide semiconductor field effect transistor (MOSFET) solution. The internal smart bootstrap switch prevents overcharging of the BOOST pin to SW pin high-side driver supplies during dead times, protecting the gate of the top GaN FET. The LTC7891 internally optimizes the gate driver timing on both switching edges to achieve smart near zero dead times, significantly improving efficiency and allowing for high frequency operation, even at high input voltages.
Figure 2. Efficiency and Power Loss vs. Load Current
Alternatively, the user can adjust the dead times with external resistors for margin or to tailor the application. Note that throughout this data sheet, multifunction pins, such as PLLIN/SPREAD, are referred to either by the entire pin name or The gate drive voltage of the LTC7891 can be precisely adjusted by a single function of the pin, for example, PLLIN, when only that from 4 V to 5.5 V to optimize performance, and to allow the use of function is relevant. different GaN FETs, or even logic level MOSFETs.
Rev. A DOCUMENT FEEDBACK
Information furnished by Analog Devices is believed to be accurate and reliable "as is". However, no responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other rights of third parties that may result from its use. Specifications subject to change without notice. No license is granted by implication or otherwise under any patent or patent rights of Analog Devices. Trademarks and registered
TECHNICAL SUPPORT
trademarks are the property of their respective owners. All Analog Devices products contained herein are subject to release and availability. 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