Charging System Safety Circuit
The ISL9211 is an integrated circuit (IC) optimized to provide
a redundant safety protection to a Li-ion battery 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
N-channel MOSFET to remove the power from the charging
system to the battery. In addition to the above protected
parameters, 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 ISL9211 has triple-level
protection and is two-fault tolerant.
The IC is designed to turn on the internal NFET slowly to
avoid inrush current at power up but will turn off the NFET
quickly when the input is overvoltage in order to remove the
power before any damage occurs. The ISL9211 has a logic
flag output to indicate a fault condition.