Design Of Protection Circuit With High Characteristics Used For Double-series Li-Ion Battery

As the rapid development of portable electronic applications, the long cycle lifeand the large weight ratio are its superiority, the same as low self-discharge rate and nomemory. Besides, take advantage of the low average output voltage and environmentalfriendly, The Li-Ion battery is used in lots of electronic products. In order to keep itfrom overcharge, over discharge and the overload current, the IC protector is necessary.The IC used for2-series Li-Ion battery is presented in this paper.In the first place,the system configuration is designed, and then on the basis of the system configuration,the delay circuit, control circuit, charge detection circuit and other kinds of circuits aredesigned. The chopped modulator is used to compensate the effect caused by therandom error and improve the accuracy of the voltage reference. Finally, sub-moduleslayouts and overall layout have been shown, area of whole layout is0.8mm×0.9mm.Inorder to improve the yield during practical production, some kinds of ways have beenused to compensate effect caused by the parasitic parameter and improve the matchingattribute and coupling of the signal, such as root device, crossing, dummy device andcommon-centriod method.The circuit is based on0.25μm BICMOS process, EDA simulation tools have beenused to complete simulation analysis of partial and overall circuit It demonstrated thatthe voltage of overcharge detection is4.30V, the voltage of handling overchargedetection is4.08V, the voltage of over discharge detection is2.39V, the voltage ofhandling over discharge detection is3.05V, the voltage of over current detection ofbattery1is200mV, the voltage of over current detection of battery2is1.2V, the time ofovercharge detection is1.17555s. Respectively, the time of handling overcharge anddischarge detection is36.736ms and146.944ms. In addition, the time of over currentdetection of battery1is9.184ms, the time of over current detection of battery2is4.59ms, and the time of handling over current detection is287μs. The power dissipationis6.98μA. The theoretical analysis and simulation results show that the functions of thechip meets design specifications.