Description
The A8509 is a multi-output white LED driver for backlighting LCD panels. It integrates a current-mode boost controller and four individual current sinks.
The boost controller architecture allows for significant scaling of boost voltage to optimize the solution for the required number of LEDs per string. The FSET/SYNC pin either sets the required boost switching frequency or synchronizes the value in the range of 300 to 800 kHz.
The LED sink current value is set by an external ISET resistor (see figure 1). The four LED sinks can also be combined to achieve even higher current per LED string.

Features and Benefits
• Four integrated high current sinks for LED strings; can be
   tied together for even higher currents
• Fixed frequency current mode control with integrated gate
   driver / boost controller; powerful gate driver to drive an
   external N-channel MOSFET allows significant scaling
   capability on the number of LEDs per string
• Parallel operation with one boost controller (master) and
   up to three additional slave controllers; can run up to
   16 strings of LEDs while populating only a single master
   boost regulator
• Active current sharing between LED strings for
   0.7% accuracy and 0.8% matching
• Wide input voltage range: 9 to 40 V
• Internal bias supply for single-supply operation (typically
   VIN = 12 or 24 V)
• Separate Enable and PWM pins as interface for Enable
   and PWM Dimming functions
• Fset/ Sync function to either set the boost converter
   switching frequency or synchronize at up to 800 kHz
• Protection Features
   ▫ Open or shorted LED pin protection
   ▫ Open Schottky protection
   ▫ Pulse-by-pulse current limit
   ▫ Overtemperature protection (OTP)