Features

• Step-Up/Step-Down Fractional Charge Pump for Up to 92% Efficiency
• Independent Current and Dimming Control for 1-4 LED Main, 1-2 LED Sub and RGB LED Displays
• LED Currents Programmable Using 3-Wire Serial Interface
• Up to 250mA of Continuous LED Current
• 0.7% LED Current Matching
• Low Noise Constant Frequency Operation*
• Minimal Component Count
• Automatic Soft-Start Limits Inrush Current
• Four Programmable Dimming States for Main and Sub Displays
• Up to 4096 Color Combinations for RGB Display
• Low Shutdown Current: I_CC < 1µA
• Tiny 24-Lead (4mm x 4mm) QFN Package

Typical Application

Description

The LTC3205 is a highly integrated multidisplay LED controller. The part contains a high efficiency, low noise fractional step-up/step-down charge pump to provide power for both main and sub white LED displays plus an RGB color LED display. The LTC3205 requires only four small ceramic capacitors plus two resistors to form a complete 3-display LED power supply and current controller.

Maximum currents for the main/sub and RGB displays are set independently with a single resistor. Current for each LED is controlled with an internal current source. Dimming and ON/OFF control for all displays are achieved via a 3-wire serial interface. Four dimming states exist for the main and sub displays and 16 dimming states are available via internal PWM for the red, green and blue LEDs resulting in up to 4096 color combinations.

The LTC3205 charge pump optimizes efficiency based on V_IN and LED forward voltage conditions. The part powers up in step-down mode and automatically switches to stepup mode once any enabled LED current source begins to enter dropout. Internal circuitry prevents inrush current and excess input noise during start-up and mode switching.

The LTC3205 is available in a low profile 24-lead (4mm x 4mm x 0.8mm) QFN package.