TUTORIALS 5801

USB Battery Charging and Adapter Emulators

By: Mohamed Ismail

Abstract: At home, in the car, or plugged into a computer, USB-powered portable equipment needs a smart method for determining the appropriate amount of power to draw for both normal operation and charging. Motivated by the huge variety of portable devices, differences in USB ports, and complicated nature of rechargeable batteries, the USB Battery Charging Specification Revision 1.2 is a critical standard for establishing the proper way to charge a battery from a USB port. But even with the BC1.2 specification, some portable device manufacturers have still implemented proprietary chargers, further complicating the field of USB battery charging. This article discusses the impetus for recent industry standards for USB battery charging and the specifications that each defined. It also presents simple strategies for implementing a USB port capable of high-current charging for a variety of proprietary portable devices.