As the power requirements of portable devices become bigger and bigger,which forces to increase the battery capacity to provide longer usage time to meet the demand. This gives designers a series of challenges, including how to reduce charging time of these larger battery, minimizing heat dissipation during charging, and supportting for USB-OTG host function enhancements. To solve these problems, the world's leading high-performance power and portable products supplier,Fairchild Semiconductor works with customers to develop a comprehensive USBOn-The-Go (USB-OTG) support FAN5401x series USB-compatible Li-Ion switch mode battery charger. This series of products is based on switch-mode topology from FAN5400 series ,the first device FAN54013 provides up to 1.45A and higher maximum charging current, and greater USBOTG boost power, which can support all at 5V 500mA current. Besides switch-mode topology, while charges through the USB port or AC / DC adapter for a single or dual lithium-ion (Li-Ion) battery, FAN54013 can shorten the charging time and work out the a linear charger thermal problems .New products have a variety of typical applications, including mobile phones, smart phones, tablet PCs, wireless broadband hotspots, digital cameras and portable media / game players and other portable products in single or dual lithium-ion batteries. In addition to providing the highest efficiency of 94% for the charge, FAN54013 has a set of protection features, including an integrated 20V nominal input voltage, thermal protection, reverse current blocking, watchdog timer, and accurate input current limit of + / -5% that meets USB requirements .The operation of USBOTG  uses integrated 5V500mA boost regulator and shares the same inductance with the charger , reducing external component.