Introduction
This document discusses the AAT4291 RGB EVAL evaluation board and the application of the AAT4291 as an RGB LED driver. Advanced RGB LED control is realized without having to use multiple discrete MOSFET switches controlled by multiple I/O pins from the system processor. Only one digital I/O pin is needed for complete, independent brightness control of each of the R, G, and B LEDs.

The AAT4291 SmartSwitch™ is a member of AnalogicTech’s Application Specific Power MOSFET™ (ASPM™) product family. The AAT4291 has three P-channel MOSFETs configured for use as a microprocessor I/O expander. Having independent drain outputs and a common input, the AAT4291 operates with an input voltage ranging from 1.8V to 5.5V, making it ideal for 2.5V, 3.3V, or 5V systems, as well as systems powered by lithium-ion/polymer batteries. Each switch features a fast 500ns turnon time. The switch states are controlled by the Simple Serial Control™ (S2Cwire™) serial digital interface. The quiescent supply current is very low, typically 5µA. In shutdown mode, the supply current is reduced to less than 1µA.