White LED Step-Up ConverterDescriptionThe IZ1937 is a step-up DC/DC converter specifically designed to drive white LEDs with aconstant current. The device can drive two, three or four LEDs in series from a Li-Ion battery.Series connection of the LEDs provides identical LED currents resulting in uniformbrightness and eliminating the need for ballast resistors. The IZ1937 operates at 1.2MHz,allowing the use of tiny external components. The output capacitor can be as small as0.22uF, saving space and cost versus alternative solutions.A low 95mV feedback voltage minimizes power loss in the current setting resistor for betterefficiency.The device can used in mobile phones, PDAs, Handheld Computers, calculators, digitalcameras, MP3-players, GPS-receivers.Features• Internally determined LED current• High Efficiency: 84% Typical• Drives Up to 4 LEDs from a 3.2V Supply• Drives Up to 6 LEDs from a 5V Supply• 36V rugged bipolar switch• Fast 1.2MHz switching frequency• Uses tiny 1mm Tall Inductors• Requires only 0.22uF output capacitor