Use of white-LED drivers has increased in recent years due to the popularity of color LCD screens on most portable electronic equipment. The white backlight required to bring out the color in these screens is most often provided by white LEDs. In applications powered by a one-cell Li-ion battery， charge pumps or boost converters have been required to drive these LEDs because of their high forward voltage （4 V typical）。 As white-LED technology has advanced， the forward voltage required has significantly dropped. Today， white LEDs such as Nichia’s NHSW046 or NSSW100C are available with a typical forward voltage of less than 3 V. The lower forward voltage eliminates the need for voltage boosting， permitting the use of linear regulation topologies that reduce costs and solution size and increase efficiency across the battery-discharge range. Figure 1 compares the efficiency and battery voltage of the Texas Instruments TPS7510x and a typical series LED boost