The BL4054B-42TPTRN is an electronic power management integrated circuit (PMIC) manufactured by Belling. It is a TSOT23-5 RoHS package and can be used to manage secondary batteries in consumer and industrial electronics. The BL4054B-42TPTRN can be used to monitor, protect, and control secondary batteries to prolong the life of the battery. It has an over-charge protection circuit, a short-circuit protection circuit, and an over-discharge protection circuit suitable for most single-cell Li-ion, Li-polymer, and Li-Fe batteries. It also has a low battery voltage detection circuit, a manual reset timer circuit, and a thermal protection circuit. The BL4054B-42TPTRN has a low quiescent current of 0.7 µA and a high current source capability of 40 mA. It is a cost-effective solution for battery management applications such as cell phone, laptop, and tablet.