AP3039 is a current mode high voltage low-side Nchannel MOSFET controller which is ideal for boost regulators. It contains all the features needed to implement single ended primary topology DC/DC converters. The input voltage range of AP3039 is from 5V to 27V. Its operation frequency is adjustable from 150kHz to 1MHz. The AP3039 has UVLO (Under Voltage Lock Out) circuit. It uses two external resistors to set the UVLO voltage. The AP3039 also has an over output voltage protection to limit the output voltage. The OVP voltage can be set through external resistors. If the output voltage is higher than the OVP high threshold point, it will disable the driver, when the output voltage drops to the OVP low threshold point, it will enable the driver. It also features a soft start to reduce the inrush current when power on, the soft start time can be set through an external capacitor.