LT1932 Datasheet | Linear Technology

Features s Up to 80% Efficiency s Inherently Matched LED Current s Adjustable Control of LED Current s Drives Five White LEDs from 2V s Drives Six White LEDs from 2.7V s Drives Eight White LEDs from 3V s Disconnects LEDs In Shutdown s 1.2MHz Fixed Frequency Switching s Uses Tiny Ceramic Capacitors s Uses Tiny 1mm-Tall Inductors s Regulates Current Even When VIN > VOUT s Operates with VIN as Low as 1V s Low Profile (1mm) Thin SOTTM Package U APPLICATIO S s Cellular Telephones s Handheld puters s Digital Cameras s Portable MP3 Players s Pagers TYPICAL APPLICATIO Li-Ion Driver for Four White LEDs VIN 2.7V TO 4.2V L1 6.8µH D1 C1 4.7µF PWM DIMMING CONTROL VIN SW 5 SHDN 3 LED RSET RSET 1.50k 15m A C1: TAIYO YUDEN JMK212BJ475 C2: TAIYO YUDEN EMK212BJ105 D1:ZETEX ZHCS400 L1: SUMIDA CLQ4D106R8 OR PANASONIC ELJEA6R8 Constant-Current DC/DC LED Driver in Thin SOT DESCRIPTIO The LT®1932 is a fixed frequency step-up DC/DC converter designed to operate as a constant-current source. Because it directly regulates output current, the LT1932 is ideal for driving light emitting diodes (LEDs) whose light intensity is proportional to the current passing through them, not the voltage across their terminals. With an input voltage range of 1V to 10V, the device works from a variety of input sources. The LT1932 accurately regulates LED current even when the input voltage is higher than the LED voltage, greatly simplifying batterypowered designs. A single external resistor sets LED current between 5m A and 40m A, which can then be easily adjusted using either a DC voltage or a pulse width modulated (PWM) signal. When the LT1932 is placed in shutdown, the LEDs are disconnected from the output, ensuring a quiescent current of under 1µA for the entire circuit. The device’s 1.2MHz switching frequency permits the use of tiny, low profile chip inductors and capacitors to minimize footprint and cost in space-conscious portable applications. , LTC and...