LED Charge Pumps Get Smarter

Five tri-mode, high-efficiency charge pumps for white LED backlight and color LED applications combine a load switch (13) and a high-efficiency (1.53 or 23) charge pump with an internal sensing circuit that monitors the required voltage on each constant current-sink input. The load switch and charge pump modes are set based on the input battery voltage and current sink input voltage. Advanced Analogic Technologies' AAT3151/2/3/6 products can drive four or six individual LEDs with a maximum current of 30 mA per channel. They use the company's proprietary single-wire control interface to control current level for the LED channels. Each device requires only four external components: two small 1-µF ceramic capacitors for the charge pump flying capacitors, one 1-µF ceramic input capacitor, and one 0.33- to 1-µF ceramic charge-pump output capacitor. Meanwhile, the AAT3129 charge pump provides a single current source to deliver a regulated current to drive red, green, and blue LEDs, which have dramatically different forward-voltage requirements, via three internal switches. The single-wire serial interface is used to enable, disable, and set the duty cycle of each internal MOSFET switch. The AAT3151 and AAT3152 devices, in 12-pin 3- by 3-mm DFNs, cost $1.74 and $1.70, respectively. The AAT3153 and AAT3156 parts, in 16-pin 4- by 4-mm QFNs, sell for $1.86 and $1.90. The AAT3129 devices, in 12-pin TSOPJWs, sell for $1.58. All prices are based on 1000-unit quantities.