As an example, this circuit using the LM3405A is designed to drive one InGaN WLED cycling at 4 different current levels: 0, 125mA, 250mA, and 700mA with a peak-to-peak ripple current of 40mA or less. The input is 4.2V to 4.5V from 3 AA batteries, the Vo is approximately 3.7V at 700mA current, and the switching frequency is 1.6MHz (typical). For a complete look at this reference design, visit the LED reference design library at www.ti.com.