Description
The YB1521 is a step-up DC-DC converter which operating as current source to drive up 45 white LEDs (3S15P) in parallel / series configuration from a 5V system rail. Series connecting of LEDs provides identical LED currents resulting in uniform brightness and eliminating the need for ballast resistors. The light intensity of these LEDs is proportional to the current passing through them. The YB1521 is a fixed frequency of 1.3MHz, allowing the use of tiny low profile inductors and capacitors to minimize footprint and cost in space consideration applications for cellular phone backlighting or other hand held equipment.

Features
■ 2.5V to 5.5V Input Voltage Range
■ Built In Power MOSFET
■ Drive Up to 15V @400mA at 5V Vin
■ Less than 1µA Shutdown Current
■ Up to 94% efficiency
■ Over Voltage Protection@18V
■ UVLO, Thermal Shutdown
■ Internal 1.6A Current Limit
■ 200mv Low Reference Voltage
■ Built In Soft Start
■ PWM Dimming
■ SOT23-5 Package
■ Green Package (RoHS) Available

Applications
■ Cellular and Smart Phones
■ Handheld Computers and PDAs
■ Small LCD Displays
■ GPS Terminals
■ MP3 Players
■ Digital Still and Video Cameras
■ Electronic Books