Design Of One Cell Lithium Battery Protection Chip

With the development of micro-electronic technology, the numbers of small size devices increase, such as mobile phone, pad and digital camera. And it comes up with higher demand for Li-ion battery. Because of lots of advantages, lithium batteries are used by more and more people. Compared with other batteries, Li-ion battery has many outstanding features, for example, high energy power density, high supply voltage, long working life, good safety performance, fast charge rate, strong adaptability to temperature and green environmental protection. But temperature issue makes decline easier for Li-ion battery capacity. And Li-ion battery can not afford over temperature, over discharge and overcharge. Lithium ion battery used in wrong way will even lead to blast. Those disadvantages make the protection of lithium battery more important.This paper designed a chip with high integration, high precision and low power consumption for lithium-ion battery protection. This MOSFET was integrated in the chip, equivalent impedance is 54m?RDS(ON). It can work with only an external capacitance, and that is very convenient. The integration level of this chip is higher than other lithium battery protection chip. At the same time, the chip used trimming resistors network to improve the precision of band gap reference voltage, which will improve the precision of chip. The range of voltage precision is-10mV~+10mV. To decrease current depletion, the chip designed two kind of sleeping mode(sleeping mode 1 and sleeping mode 2). The sleeping mode 1 is that the system voltage is below the over discharge detection voltage, the chip will close related current comparators to minimize the power consumption of the chip. The sleeping mode 2 is that temperature is above 120 ℃, the system will shut down most of the analog modules in order to reduce the power consumption of the chip, meanwhile it reduces temperature of chip appropriately. On normal working condition, typical current value is 2.04 uA. On sleeping mode, maximum value is 0.1uA.Compared with other lithium battery protection chip, this chip has the function of over temperature protection. And over temperature protection module uses external hysteresis, which means different reference voltages come form different output voltages. It not only can improve the precision, but also cuts down difficulty of design. Meanwhile, it still has the basic protection function, such as over charge voltage protection, over discharge voltage protection, over charge current protection and over discharge current protection, and its working current depletion is quite low. It’s suit for all electronic products requiring lithium ion battery.The chip uses 0.25 um BCD manufacturing process of CSMC. Circuit design uses Spectre software of Cadence for simulation. Layout design uses caliber for DRC, ERC, LVS verification. All simulation finished in VDD=3.5V. Whole simulations of system function match expect design.