LM3509SD

• Product Introduction

The LM3509 current-mode boost converter provides two separate outputs. The first output (main) is a constant irradiation current that drives the series white LEDs. The second outut (SUB/FB) is a configurable series of white LED biases set as a feedback pin for a constant irrigation current or constant output voltage to power the OLED panel.

When configured with a dual-output white LED bias power supply, the LM3509 adaptively adjusts the power supply voltage of the LED string to maximize efficiency and ensure that the current suck is regulated. The maximum current per output is through an external low-power resistor. An I2C-compatible interface with independently adjustable LED current, both from 0 to a maximum of 32 exponential step current outputs. When configured as a white LED + OLED bias power supply, the LM3509 can drive a string of 5 white LEDs and OLED panels at the same time to provide a constant output voltage up to 21V.

If the output overvoltage protection function is turned off on the device, the above allows the use of a small low-voltage output capacitor of 21V, V OUT rises. The LM3509 is available in a small, 10-pin, thermally enhanced LLP package that operates over the -40°C to +85°C temperature range.

LM3509SD EV kit setup to drive 2 strings of 5 white LEDs (OSRAM, LW_M67C, at 20mA V F = 3.6V). These set 5 LEDs for the main string and 5 LEDs for the group string. In addition, the resistor can be installed in the R1 and R2 pads to enable the voltage output of the OLED device to be a boost converter that displays the power supply (output voltage setting OLED (mode). Please refer to the LM3509 datasheet and application notes.

Peculiarity:

• Integrated OLED display power supply and LED driver
• Drives up to 10 LEDs at 30 mA
• The driver is powered by LEDs at 20mA and provides up to 40 mA to 21V
• More than 90% efficiency
• 32 Exponential dimming steps
• 0.15% accurate current matching between strings
• Internal soft start limits inrush current
• The True Shutdown function of the LEDs is isolated
• Input voltage range from 2.7V to 5.5V
• 21V overvoltage protection
• 1.27MHz fixed frequency operation
• Thin 10-Pin LLP Package (3× 3 ×0.8 mm)
• Universal I/O
• Active low hardware reset

Applications:

• Dual display backlight in portable applications
• Large format LCD backlight
• OLED panel power supply