LM3501TL-16EV

User's Guide SNVA084A – May 2004 – Revised April 2013 AN-1318 LM3501 Evaluation Board 1 Introduction The LM3501 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 = VFB/R2. VFB is determined by the voltage applied to the CNTRL pin. The maximum value of VFB is 0.515V and occurs with a CNTRL voltage of approximately 2.7V. This condition translates into approximately 20mA LED current. A lower CNTRL voltage will translate into a lower VFB voltage and a lower LED current. The feedback voltage can be calculated using the equation VFB = 0.191 × CNTRL. A CNTRL voltage of 125mV or greater turns the LEDs on while a CNTRL voltage of 75mV or less turns the LEDs off. Please note that for correct operation the SHDN pin must have a voltage greater than 1.1V applied to it. 2 Schematic L 22 PH VIN 2.7V - 5.5V Analog Voltage Control B1 VIN A3 CIN PF Ceramic >1.1V