General Description
The AAT3151B is a low noise, constant frequency charge pump DC/DC converter that uses a dual mode load switch (1X) and fractional (1.5X) charge pump conversion to maximize efficiency for white LED applications. The AAT3151B is capable of driving four white LEDs at a total of 120mA 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) makes the AAT3151B 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
• Dual Mode 1X and 1.5X Charge Pump for Maximum Efficiency and VF Coverage
• Drives Four Channels of LEDs
• No Inductors, Low Noise Operation
• 1MHz Constant Switching Frequency
• Small Application Circuit
• Built-In Thermal Protection
• Built-In Auto-Disable for Short-Circuit
• Automatic Soft Start
• IQ <1µA in Shutdown
• TDFN33-12 Package

APPLICATIONs
• Color (RGB) Lighting
• Programmable Current Sinks
• White LED Backlighting
• White Photo Flash for Digital Still Cameras