General Description

The MIC3289 is a PWM boost-switching regulator that is optimized for constant-current white LED driver applications. The MIC3289 features an internal Schottky diode, allowing an efficient DC/DC solution that requires only 4 external components.

The MIC3289 allows for a single wire simple digital interface to control the dimming over 16 steps with a log scale to give better resolution at the lower currents and to better match the sensitivity of the human eye. The preprogramming feature allows the user to select any one of the 16 WLED current levels as the start-up brightness level.

The feedback voltage of the MIC3289 is only 250mV, allowing high efficiency while retaining excellent accuracy for the white LED current.

The MIC3289 implements a constant frequency 1.2MHz PWM control scheme. The high frequency PWM operation saves board space by reducing external component sizes. The 1.2MHz PWM scheme also reduces switching noise and ripple to the input power source.

The 2.5V to 6.5V input voltage range of MIC3289 allows direct operation from single cell Li Ion as well as 3- to 4-cell NiCad/NiMH/Alkaline batteries. Battery life is preserved with a low 1µA shutdown current.

Features

• Single wire combines 16 level logarithmic brightness & shutdown control

• 16V / 24V OVP options supports up to 4 & 6 WLEDs

• Start-up in any one of 16 brightness levels

• Internal Schottky diode

• 2.5V to 6.5V input voltage

• 1.2 MHz PWM operation

• Over 500mA switch current

• 250mV reference voltage

• ±5 LED current accuracy

• <1µA shutdown current

• Over temperature protection

• UVLO

• Thin SOT23-6L package option

• 2mm × 2mm leadless MLF®-8L package option

• –40°C to +125°C junction temperature range

Applications

• White/Blue LED driver for backlighting

- Cell phones

- PDAs

- GPS systems

- Digital cameras

- Multimedia / MP3 players

• LED flashlights

• Constant current power supplies