General Description
The AAT3157 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 AAT3157 is capable of driving up to three channels of LEDs at 20mA per channel 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 IN and OUTCP) 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 Current Levels
    — 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 up to Three Channels of LEDs
• No Inductors, Low Noise Operation
• 1MHz Constant Switching Frequency
• Small Application Circuit
• Built-In Thermal Protection
• Automatic Soft Start
• IQ <1µA in Shutdown
• 2.85x3.0mm TSOPJW-12 Package

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