LTC3490

U U LTC3490 Single Cell 350mA LED Driver FEATURES ■ 350mA Constant Current Output ■ 2.8V to 4V Output Compliance ■ 1- or 2-Cell NiMH or Alkaline Input ■ Synchronous Rectification: Up to 90% Efficiency ■ Fixed Frequency Operation: 1.3MHz ■ Low Quiescent Current: <1mA ■ Very Low Shutdown Current: <50µA ■ Open LED Output Limited to 4.7V ■ VIN Range: 1V to 3.2V ■ Dimming Control ■ Undervoltage Lockout to Protect Batteries ■ Low Profile (0.75mm) 3mm × 3mm Thermally Enhanced 8-Lead DD and S8 Packages U APPLICATIO S ■ Portable Lighting ■ Rechargeable Flashlights DESCRIPTIO The LTC®3490 provides a constant current drive for 1W LED applications. It is a high efficiency boost converter that operates from 1 or 2 NiMH or alkaline cells and generates 350mA of constant current with up to 4V of compliance. It contains a 100mΩ NFET switch and a 130mΩ PFET synchronous rectifier. The fixed switching frequency is internally set to 1.3MHz. The LTC3490 limits the output voltage to 4.7V if the output load is disconnected. It also features an analog dimming capability that reduces the drive current proportional to the CTRL/SHDN pin voltage. A low-battery logic output signals when the battery has dropped below 1V/cell. An undervoltage lockout circuit shuts down the LTC3490 when the battery voltage drops below 0.85V/cell. The feedback loop is internally compensated to minimize component count. , LT, LTC and LTM are registered trademarks of Linear Technology Corporation. All other trademarks are th...