The LM3509 is a high efficiency current mode boost converter designed for driving white LED's and/or OLED displays. It offers dual current sinks and I2C compatible brightness control. The LM3509 can be configured as a constant current sink for driving series white LED's or as a feedback pin to set a constant output voltage for powering OLED panels. When configured as a dual output white LED bias supply, it adaptively regulates the supply voltage of the LED strings to maximize efficiency and ensure the current sinks remain in regulation. The maximum current per output can be set via a single external low power resistor. The LED current in each output can be independently adjusted from 0 to max current in 32 exponential steps using the I2C compatible interface. When configured as a white LED + OLED bias supply, the LM3509 can independently and simultaneously drive up to 5 white LED strings and provide a constant output voltage of up to 21V for OLED panels. Output over-voltage protection shuts down the device if VOUT rises above 21V, allowing for the use of small sized low voltage output capacitors. The LM3509 is offered in a small 10-pin thermally enhanced LLP package and operates over the -40°C to +85°C temperature range.
The LM3509 is a current‑mode boost converter that provides two independent constant‑current sinks for driving white LEDs and OLED panels. One sink (MAIN) can drive up to 10 LEDs at 30 mA, while the second sink (SUB/FB) can be used as a constant‑current LED bias or as a feedback pin for a constant‑voltage OLED supply.
The device operates from a 2.7 V to 5.5 V input, delivers up to 21 V output for OLED panels, and offers over‑90 % efficiency. It features 32 exponential I²C‑compatible dimming steps, accurate current matching, soft‑start, and built‑in over‑voltage protection, all in a low‑profile 10‑pin LLP package.
| Input Voltage Range | 2.7 V to 5.5 V |
|---|---|
| Efficiency | >90 % |
| Dimming Steps | 32 exponential steps |
| Current Matching Accuracy | 0.15 % between strings |
| Switching Frequency | 1.27 MHz (typical) |
| Package Size | 8 mm × 3 mm × 0.8 mm (10‑pin LLP) |
The LM3509 operates from 2.7 V to 5.5 V input.
The device provides 32 exponential I²C‑compatible dimming steps.