Boost regulator for LED backlight strings
The LM3503SQX-35 is a step-up (boost) DC-DC regulator from Texas Instruments, designed specifically for driving LED backlight strings in small-format displays.
Dimming flexibility: Analog and PWM
The regulator supports both analog and PWM dimming, giving the system designer two independent paths for brightness control. Analog dimming adjusts the LED current linearly via a control voltage; PWM dimming modulates the switch duty cycle at a frequency independent of the 1 MHz switching rate. This dual-mode capability is a practical advantage when the host processor's PWM peripheral is already allocated or when the application demands flicker-free analog dimming at low brightness levels.
Obsolete — planning the replacement path
For new designs or BOM sustainment, a direct pin-compatible replacement is not listed in the official record. The base product number LM3503 family may include other output-voltage variants (e.g., LM3503SQX-30 for 30 V), but these share the same obsolescence status.
Housed in a 16-WFQFN with exposed pad (4x4 mm body), the LM3503SQX-35 requires a thermal land pattern on the PCB to dissipate heat from the internal switch.