Preliminary PT6905 3-Stage Dimming LED Driver DESCRIPTION The PT6905 is a continuous mode inductive step-down converter with three-stage dimming, designed for driving single or multiple series white LEDs efficiently from a voltage source higher than the output LED voltage. The IC operates from an input supply between 6V and 36V and provides three-stage dimming with output current of up to 1.2Amp. The PT6905 includes the internal switch and a high-side output current sensing circuit, which uses an external resister to set the average output current. The PT6905 has a three-stage dimming function. That is to say the output current will be adjusted to 100% when the first time power on corresponding to stage-one, 30% when the second time power on corresponding to stage-two and 10% when the third time power on corresponding to stage-three. The cycle will restart to stage-one again when the fourth time power on. So this cycle will go on if the power off time is no less than six seconds according to the external capacitor Cs of 10μF. And the power could be saved if less light needed. FEATURES • • • • • • • High Efficiency (up to 95%) Maximum 1.2A Output Current Wide Input Voltage: 6V ~ 36V Three-Stage Dimming Typical 5% Output Current Accuracy Thermal Shutdown 150℃ Typical SOT-89-5L Package APPLICATIONS • DC/DC LED Driver • Low Voltage Industrial LED Lighting • Low Voltage Halogen Replacement LEDs • Decorative LED Lighting • LED Table Lighting BLOCK DIAGRAM Tel: 886-66296288‧Fax: 886-29174598‧ http://www.princeton.com.tw‧2F, 233-1, Baociao Road, Sindian, Taipei 23145, Taiwan PT6905 TYPICAL APPLICATION PRE1.1 2 May 2010 PT6905 ORDER INFORMATION Valid Part Number PT6905 Package Type SOT-89-5L Top Code PT6905 PIN CONFIGURATION PIN DESCRIPTION Pin Name LX GND VRGS ISNS VIN Exposed PAD PRE1.1 Description Drain of The Internal NMOS Switch Signal Ground Output of Internal Regulator Voltage of Logic Inductance Current Sense Pin Input Supply Pin. Must be locally bypassed. Power Ground 3 Pin No. 1 2 3 4 5 May 2010 PT6905 IMPORTANT NOTICE Princeton Technology Corporation (PTC) reserves the right to make corrections, modifications, enhancements, improvements, and other changes to its products and to discontinue any product without notice at any time. PTC cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a PTC product. No circuit patent licenses are implied. Princeton Technology Corp. 2F, 233-1, Baociao Road, Sindian, Taipei 23145, Taiwan Tel: 886-2-66296288 Fax: 886-2-29174598 http://www.princeton.com.tw PRE1.1 4 May 2010