AN-1309| Application Note
LM3500 Evaluation Board
LM3500 Evaluation Board
National Semiconductor Application Note 1309 Clinton Jensen December 2003
Introduction
The LM3500 is a synchronous step-up DC/DC converter designed for white LED applications. The evaluation board is set up to drive 3 standard VF white LEDs from a single Li-Ion battery. A fourth LED pad (D4) is included for testing of up to 4 low VF white LEDs.
The LED current is set using the resistor R2 and the equation ILED = 0.5V/R2. The evaluation board comes set up for approximately 20 mA LED current. Please note that for correct operation the SHDN pin must have a voltage greater than 1.1V applied to it.
Schematic
20092801
Bill of Materials
Designator U1 L CIN COUT D1 D3 D4 R1 Component LM3500TL-ADJ, uSMD 8-lead 22 uH, DT1608C-223 1 uF, 25V Ceramic C3216X7R1E105K 1 uF, 25V Ceramic C3216X7R1E105K White LED, LWT67C 0 Resistor, 1206 Case, CRCW1206 000J 24, 1206 Case, CRCW1206 240J Manufacturer National Semiconductor Coilcraft TDK TDK Osram Vishay Vishay
AN-1309
2004 National Semiconductor Corporation
AN200928
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