Research And Optimization Of A Linear Li-ion Battery Charge Management Chip

As Li-ion batteries have less weight,smaller size and higher available energy densities than its counterparts in the battery system (such as NiCd,NiMH),they are very suitable for portable electrical applicances. Recent market reports reveal that quantity demanded of Li-ion batteries has exceeded a billion every year. So it is well worth doing research on the design of the Li-ion batteries power management chip.This thesis firstly described the system architecture of the chip. This system employed linear current-limited and constant-voltage battery charging mode and technology of integrated powerFET. So it can decrease heat productivity from the chip and external components to build up battery charging system. This chip must work with the current-limited adapter and it is ideal for single Li-ion batteries. It has better than 0.5% voltage regulation accuracy. When the battery's voltage falls bellow the preset recharge threshold,the chip will recharge the battery automatically. When the power is removed from the system,the chip will enter into the sleep mode to gain a low quiescent current. And then, the subcircuits such as bandgap reference,pre-charging¤t-limited charing circuit,current-sensing circuit,constant-voltage charing circuit,gate driver circuit for powerFET are introduced in details and corresponding simulating results are gived.The project is fabricated with the UMC BCD 0.6μm process,the simulation result has shown that the circuit works well and every electrical characteristic meets the specification of the chip.