Datasheet ALT80600 (Allegro) - 3

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LED Driver with Pre-Emptive Boost ALT80600 for Ultra-High Dimming Ratio and Low Output Ripple Table of Contents
Features and Benefits ... 1 Switching Frequency Dithering ... 14 Description .. 1 Clock Out Function.. 14 Applications ... 1 LED Current Setting .. 15 Package ... 1 PWM Dimming ... 15 Selection Guide ... 2 Pre-Emptive Boost (PEB) ... 16 Absolute Maximum Ratings ... 2 Analog Dimming with APWM Pin... 18 Thermal Characteristics .. 2 Extending LED Dimming Ratio.. 19 Typical Application – SEPIC .. 3 Analog Dimming with External Voltage... 19 Functional Block Diagram ... 4 VDD .. 20 Pinout Diagram and Terminal List ... 5 Shutdown... 20 Electrical Characteristics ... 6 Fault Detection and Protection ... 21 Functional Description .. 9 LED String Partial-Short Detect .. 21 Enabling the IC ... 9 Boost Switch Overcurrent Protection ... 22 Powering Up: LED Detection Phase .. 10 Input Overcurrent Protection and Disconnect Switch ... 23 Powering Up: Boost Output Undervoltage ...11 Setting the Current Sense Resistor ... 24 Soft Start Function .. 12 Input UVLO .. 24 Frequency Selection .. 13 Fault Protection During Operation ... 24 Synchronization .. 13 Fault Recovery Mechanism .. 26 Loss of External Sync Signal .. 14 Package Outline Drawing .. 28 Appendix A: Design Example ..A-1 L2 VSW = VIN + VOUT ≤ 50 V V D1 Breakdown voltage > 60 V IN = 4.5 to 35 V D1 L1 2.2 µF 4.7 µF L1 & L2 may be either separate or integrated 68.1 kΩ 4.7 µF 4.7 µF GATE SW OVP Vsense Vc Vin 1 µF V 10K VDD DD LED1 FAULT ALT80600 LED2 Up to 4 WLEDs in series EN (VOUT < 15 V) LED3 Up to 120 mA/ch PWM t PWM ON ≥ 0.3 µs LED4 APWM COMP CLKOUT APWM 100 kHz 0-90% AGND ISET FSET DITH PEB 220 Ω 100 pF kΩ 10 kΩ 40.2 kΩ kΩ 220 nF 8.25 10 nF 9.09
Figure 2: Typical application showing SEPIC configuration for flexible input/output voltage ratio
Allegro MicroSystems, LLC 3 955 Perimeter Road Manchester, NH 03103-3353 U.S.A. www.allegromicro.com Document Outline Features and Benefits Description Applications Package Selection Guide Absolute Maximum Ratings Thermal Characteristics Typical Application – SEPIC Functional Block Diagram Pinout Diagram and Terminal List Electrical Characteristics Functional Description Enabling the IC Powering Up: LED Detection Phase Powering Up: Boost Output Undervoltage Soft Start Function Frequency Selection Synchronization Loss of External Sync Signal Switching Frequency Dithering Clock Out Function LED Current Setting PWM Dimming Pre-Emptive Boost (PEB) Analog Dimming with APWM Pin Extending LED Dimming Ratio Analog Dimming with External Voltage VDD Shutdown Fault Detection and Protection LED String Partial-Short Detect Boost Switch Overcurrent Protection Input Overcurrent Protection and Disconnect Switch Setting the Current Sense Resistor Input UVLO Fault Protection During Operation Fault Recovery Mechanism Package Outline Drawing Appendix A: Design Example