Datasheet A80602, A80602-1 (Allegro) - 9

A80602 and High Power LED Driver with Pre-Emptive Boost A80602-1 for Ultra-High Dimming Ratio and Low Output Ripple APPLICATION EXAMPLES
VIN *optional VOUT > 40 V D1 R L1 SENSE C Q2 IN Q1 ROVP C COUT VDRV GATE VDRV GDRV CS PGND VSENSE VC VIN OVP VDRV CVDD RPU VDD VT LED1 FAULT
A80602
LED2 Cascode EN/ Transistors PWM LED3 PWM ton ≥ 0.3 µs ... Q3 .. Q8 LED6 ADIM iLED Max. LEDx pin voltage 100% COMP limited to VDRV - VT ADIM AGND ISET FSET DITH PEB RZ CP RM APWM 100 kHz 0-90% RISET RFSET CZ CM RD
Figure 4: Cascode transistors can be used in case VOUT needs to be higher than 40 V
To drive an output load with more than 11 white LEDs in series, the above application circuit can be used. The cascode transistors Q3..Q8 limits LED1-6 pin voltages to VDRV – VT, even in case of LED string direct short. (VT = threshold voltage of transistor, typically under 3 V). The cascode transistors can be any small-signal N-channel MOSFET, rated for the maximum output voltage and LED current per channel. As an example: consider T2N7002BK in SOT23 package. It is rated for 60 V breakdown and 400 mA continuous current. Allegro MicroSystems, LLC 9 955 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 LED Current Setting PWM Dimming Pre-Emptive Boost (PEB) Analog Dimming ADIM Mode APWM Mode Extending LED Dimming Ratio Analog Dimming with External Voltage VDD VDRV Shutdown Fault Detection and Protection FAULT Status LED String Partial-Short Detect Overvoltage Protection Boost Switch Overcurrent Protection Input Overcurrent Protection and Disconnect Switch Setting the Input Current Sense Resistor Input UVLO Fault Protection During Operation Package Outline Drawing Appendix: External MOSFET Selection Guide