General Description
The AAT3156 is a low noise, constant frequency charge pump DC/DC converter that uses a trimode load switch (1X), fractional (1.5X), and doubling (2X) conversion to maximize efficiency for white LED applications. The AAT3156 is capable of driving six-channel LEDs at a total of 180mA from a 2.7V to 5.5V input. The current sinks may be operated individually or in parallel for driving higher-current LEDs. A low external parts count (two 1µF flying capacitors and two small 1µF capacitors at VIN and VOUT) make this part ideally suited for small battery-powered applications.

Features
• VIN Range: 2.7V to 5.5V
• Fully Programmable Current with Single Wire
    — 16-Step Logarithmic Scale
    — 15/20/30mA Max Current
    — Four Low Current Settings Down to 50µA
    — Low IQ (50µA) for Low Current Mode
• Tri-Mode 1X, 1.5X, and 2X Charge Pump for Maximum Efficiency and VF Coverage
• Drives Six Channels of LEDs
• Individual Main/Sub-Group Control
• No Inductors, Low Noise Operation
• 1MHz Constant Switching Frequency
• Small Application Circuit
• Built-In Thermal Protection
• Built-In Auto-Disable For Open Circuit
• Automatic Soft-Start
• IQ <1µA in Shutdown
• Thermally-Enhanced QFN44-16 Package

Applications
• Color (RGB) Lighting
• Programmable Current Sinks
• White LED Backlighting
• White Photo Flash for DSCs