The series connection allows the LED current to be identical for uniform brightness. Its low on-resistance of NFET and low feedback voltage reduce power loss and achieve high efficiency. Fast switching frequency(1.5MHz typical) allows using small-size inductor and both of input and output capacitors. An over voltage protection function,which monitors the output voltage via OVP pin, stops switching of the IC if the OVP voltage exceeds the over voltage threshold. An internal soft-start circuit eliminates the inrush current during start-up.