Li-Ion Battery Charger With USB Power Manager

With the rapid growth of electronic technology, the portable electronic devices expand very speedily, so does the USB port. The popularity of USB makes it an attractive choice for charging the Li-Ion battery of the portable devices while transferring data between devices. According to the requirements, a Li-Ion battery charger with USB power manager which named XD6903 is designed in this paper on the basis of the project"Theoretical Research and Design of Key Technique for Power Management IC".The detailed system design and the circuit designs of the key sub-blocks of XD6903 are given. And the simulation of all functions and electrical characteristics are presented. A power supply selecting circuit provides a small, simple solution for obtaining power from two different power sources: a USB port and a wall adapter. The USB power controller accurately limits USB current to 500mA or 100mA. A high-accuracy band-gap voltage reference circuit using trimming meets the critical voltage requirement of Li-Ion batteries. The programmable charge current and charge time make the application of this chip more facility. By adding the constant temperature charge control based on the trickle-charge control, constant current charge control and constant voltage charge control, the charge current will be reduced by the internal thermal limit if the die temperature attempts to rise. With other control and protect circuits, the intellectualized charge control come true.Finally, the simulation has completed by using the Cadence software with the TSMC 0.6μm CMOS process. Many kinds of simulations are finished based on various spice models, operating-temperature and supply-voltage, with the results of the circuit optimized. The simulation results show that the performance in application is excellent and can meet the prospective specifications.