Features

• Charge Pump Provides High Efficiency with Automatic Mode Switching
• Multimode Operation: 1x, 1.5x, 2x
• Four Low Dropout LED Outputs
• Up to 600mA Total Output Current
• Independent Torch and Flash ISET and Enable Pins
• Low Noise Constant Frequency Operation*
• PWM Brightness Control via the EN2 Pin
• Low Shutdown Current: 4μA
• Internal Soft-Start Limits Inrush Current During Start-Up and Mode Switching
• Open/Short LED Protection
• No Inductors
• (3mm x 3mm) 16-Lead QFN Plastic Package

Typical Application

Description

The LTC3217 is a low noise charge pump DC/DC converter designed to power four high current LEDs. The LTC3217 requires only four small ceramic capacitors and two current set resistors to form a complete LED power supply and current controller.

Built-in soft-start circuitry prevents excessive inrush current during start-up and mode changes. High switching frequency enables the use of small external capacitors. Independent high and low current settings are programmed by two external resistors. Shutdown mode and current output levels are selected via two logic inputs.

The current through the LEDs is programmed via ISET1 and ISET2. In addition, the brightness can be controlled by pulse width modulation of the EN2 pin.

The charge pump optimizes efficiency based on the voltage across the LED current sources. The part powers up in 1x mode and will automatically switch to boost mode whenever any enabled LED current source begins to enter dropout. The first dropout switches the part into 1.5x mode and a subsequent dropout switches the part into 2x mode. The LTC3217 resets to 1x mode whenever the part is shut down.

The LTC3217 is available in a low profile 16-lead (3mm × 3mm × 0.75mm) QFN package.