Charging System Safety Circuit

The ISL9209C is an integrated circuit (IC) optimized to provide a redundant safety protection to a Li-ion battery from failures of a charging system. The IC monitors the input voltage, the battery voltage, and the charge current. When any of the three parameters exceeds its limit, the IC turns off an internal P-Channel MOSFET to remove the power from the charging system. In addition to the above protected parameters, the IC also monitors its own internal temperature and turns off the P-Channel MOSFET when the temperature exceeds +140°C. Together with the battery charger IC and the protection module in a battery pack, the charging system using the ISL9209C has triple-level protection and is two-fault tolerant. The IC is designed to turn on the internal PFET slowly to avoid in-rush current at power-up but will turn off the PFET quickly when the input is overvoltage in order to remove the power before any damage occurs. The ISL9209C has a logic warning output to indicate the fault and an enable input to allow the system to remove the input power.