Boost regulator for single-string LED backlight
The LM3508TL/NOPB is a step-up (boost) DC-DC regulator from Texas Instruments, purpose-built for driving a single LED string in backlight applications. It integrates the switching FET internally and delivers up to 30 mA per channel at a regulated output voltage up to 17.5 V. PWM dimming input is provided directly, so the host processor or backlight controller can vary brightness without an external PWM transistor.
850 kHz switching — inductor sizing and EMI
At this frequency the fundamental ripple sits below 1 MHz, which helps pass conducted emission limits without a complex input filter. The 5.5 V absolute max means a 5 V rail is safe — no external clamp needed.
The 0.50 mm pitch BGA requires a 2-layer or 4-layer board with micro-vias for fan-out — plan the PCB stack-up before committing the layout.