AP3502概述：2A，340KHZ，18V同步整流降压DC-DC转换器
The AP3502 is a 340kHz fixed frequency, current mode, PWM synchronous buck (step-down) DC-DC converter, capable of driving a 2A load with high efficiency, excellent line and load regulation. The AP3502 integrates N-channel power MOSFET switches with low on-resistance. Current mode control provides fast transient response and cycle-by-cycle current limit.
The over output voltage protection is equipped in AP3502, which protects the AP3502 under open load condition. The AP3502 includes UVLO, programmable soft-start and OTP to protect the circuit.This AP3502 is available in SOIC-8 package.

AP3502技术特性
• Input Voltage Range: 4.75V to 18V
• Fixed 340kHz Frequency
• High Efficiency: up to 93%
• Output Current: 2A
• Current Mode Control
• Built-in Over Current Protection
• Built-in Thermal Shutdown Function
• Built-in UVLO Function
• Built-in Over Voltage Protection
• Programmable Soft-start

AP3502应用领域
• LCD TV
• Set Top Box
• Portable DVD
• Digital Photo Frame

AP3502管脚定义：
       1)BS：自举升压脚.与SW脚用电容相连，以驱动内部MOSFET.
       2)IN：电源电压输入脚。
       3)SW：开关电源输出脚。此脚需要连接到电感和自举电容上。
       4)GND：接地脚。
       5)FB：反馈脚。此脚通过电阻分压器与sw输出的系统电压相连。当此脚电压超过0.923V正常值20%时。内部过压保护器动作；当此脚电压低于0.3V时，内部的过流保护器动作。
       6)COMP：补偿脚。此脚连接误差放大器与电流比较器，用于回路的补偿控制。
       7)EN：控制输入脚。此脚电压高于1.5V时，IC开启；此脚电压低于0.4V时，IC关闭。IC关闭期间总电流将低于1uA。
       8)SS：软启动控制输入脚。此脚外接电容器用于控制软启动时间