In this study, the current sampling method and the highly integrated switch proposed are successfully integrated into a prototype single lithium battery management chip, which was designed by the authors and fabricated with 0.18 μm 5 V technology. Fig. 13 demonstrates the die microphotograph of the chip. The proposed switch occupies 0.2829 mm 2.
The battery management chip consumes 0.838 μA of quiescent current, and its power down current is less than 10 nA. The two current detection circuits and bandgap circuits consume almost more than half of the power. This is the overhead of a single lithium battery management chip at a power supply of 3.6 V. Fig. 13. Chip microphotograph. Fig. 14.
Based on the 0.18 μm 5 V process, the circuit and the switch have been integrated into a single lithium battery management chip. The measurements show that the chip can reliably protect the battery from overvoltage, under voltage and overcurrent with low power consumption.
The proposed battery management chip had smaller charging current and quiescent current than the charging ICs. In Ref. [ 23 ], it integrated two NMOS and used the integrated NMOS as the current sampling resistor. Therefore, the values of charging and discharging overcurrent will change with the battery voltage.
A typical single lithium battery management system is mentioned in literature [ 11, 12 ], the shortcomings of those system are quite obvious. Firstly, those chips need to provide charging FET and discharging FET pins to control the corresponding switches outside the chip.
The external charging and discharging switches are integrated into the chip. Proposing adaptive substrate selecting technology, the charging switch and discharging switch can be converted into a single switch. In this paper, a highly integrated one cell battery management chip is proposed.