Charging System Safety Circuit

The ISL9211B is an integrated circuit (IC) optimized to provide a redundant safety protection to a Li-ion battery charging system. The IC monitors input voltage, battery voltage, and charge current. When any of these parameters exceeds its limit, the IC turns off an internal N-channel MOSFET to remove power from the charging system to the battery. The IC also monitors its own internal temperature and turns off the N-channel MOSFET when the temperature exceeds +150°C. Together with the battery charger IC and the protection module in a battery pack, the charging system using the ISL9211B has triple-level protection and is two-fault tolerant. The IC is designed to turn on the internal NFET slowly, to avoid in-rush current at power-up. It turns off the NFET quickly when the input is overvoltage, to remove power before damage occurs. The ISL9211B has a logic flag output to indicate a fault condition. The enable input allows the system to cut off the input power, if needed.