The Design Of Li-Ion Battery Charging Chip

Mobile phones, handheld game consoles, laptops, PDA, digital cameras and other portable electronic devices are becoming more and more popular with the increasing progress of science and technology. Most of these products are powered by the smaller Li-ion battery. The different characteristic of the Li-ion batteries and other rechargeable batteries is that a protective circuit board is in the internal. The working principle of Li-ion battery protection circuit and the specific circuit design are elaborated in this article.The Li battery is a non-rechargeable battery called primary battery, and the Li-ion battery is a rechargeable battery called secondary battery. Electronic products with large power consumption usually use the secondary battery-Li-ion battery. However, in order to get the longer life of the Li-ion battery, Li-ion battery protection chip must be used to prevent overcharge, over-discharge and discharge current of Li-ion battery.Based on the CSMC0.5um BCD process, a Li-ion battery protection chip S8204B of Japanese Seiko is reversely analyzed and designed. This article first introduced the significance and background of the subject, as well as explained the importance of the Li-ion battery protection circuit. Then under the reverse analysis process, the circuit schematic is extracted from the chip photo with the use of Chiplogic Software, every important module of the chip is analyzed and designed in Cadence. Modules mainly include the reference voltage generator module, the overcharge detection module, the over-discharge detection module, the discharge over-current detection module and so on. The specific circuit design and correct simulation results based on Specter in Cadence are given in each module, at the same time the functionality and performance simulation results of the whole circuit are given. Finally, the final design layout of the chip is given based on the CSMC0.5um BCD process, and the final layout is through design rule checking (DRC) and layout and schematic comparison (LVS).