“Intelligent charging” for Li-ion batteries

EDN Europe, 14 Dec 2007

NXP's ISP1704 and ISP1601 are USB battery charger detection chips for mobile phone designs. They detect and differentiate between a dedicated USB charger, a USB Host Charger and a USB Host when charging a mobile phone battery. The mechanism is in accordance with recently introduced regulations for the sale of mobile phones in China as well as the USB Implementers Forum (USB-IF) Battery Charging Specification Rev. 1.0. Benefits, NXP says, include faster charging and longer battery life; the features are invoked automatically whenever the consumer uses the USB connector in a mobile phone. The system has information intelligently charge a battery by determining the level of charging current that it is able to draw, based on the type of USB connection available. USB 2.0 specifications required that when a portable device is attached to a USB host or hub, the peak supply capacity was limited to 500 mA. New specs from the USB-IF now permit devices to draw current in excess of the USB 2.0 requirements and call for portable devices to be able to distinguish between a high-current wall charger (up to 1.8A), a USB host or hub charger (up to 1.5A), and a standard USB host or hub (up to 500 mA).
NXP says that the ISP1704 is the first high speed USB OTG ULPI transceiver to also offer an integrated battery charger detection function. It transmits and receives USB data at high-speed (480 Mbit/sec), full-speed (12 Mbit/sec) and low-speed (1.5 Mbit/sec) rates. The ISP1601 is a dedicated USB battery charger detection IC with an chip-scale package footprint of less than 2mm2. EDN Europe recently reported that the Open Mobile Terminal Platform (OMTP) forum had announced that its members had agreed to integrate micro-USB as a future common connector for data and charging.
Full details on the chips are here.