GENERAL DESCRIPTION

The SM8237 is a step-up DC/DC converter specifically designed to drive white LEDs with a constant current. The device can drive two, three or four LEDs in series from a Li-ion cell. Series connection of the LEDs provides identical LED currents resulting in uniform brightness and eliminating the need for ballast resistors. The SM8237 switches at 1.2 MHz, allowing the use of tiny external components. The output capacitor can be as small as 0.22μF, saving space and cost versus alternative solutions. A low 95mV feedback voltage minimizes power loss in the current setting resistor for better efficiency.

FEATURES

• Inherently matched LED current
• High efficiency : 84% typical
• Drives up to four LEDs from a 2.8V supply
• Drives up to six LEDs from a 5V supply
• 36V rugged bipolar switch
• Fast 1.2MHz switching frequency
• Uses tiny 1 mm tall inductors
• Requires only 0.22μF output capacitor
• Low profile TSOT package