Manual Adjustable LED Driver

In many electronics-level adjustments such as LED drivers for LCD panel backlight controls, we can use AD5228. A manually adjustable LED driver is shown on figure below.

The voltage across the white LED D1 is set by the AD5228 for the brightness control. A typical white LED with Vf of 3.5 V requires a resistor, R1, to limit U2 current since U2 handles up to 250 mA. This circuit is simple, but the power is not efficient. To conserve power, U2 shutdown pin can be toggled with a PWM signal. [Source: Analog Devices Application Note]