Li-Ion stack protector for 2-5 series cells
The BQ771808DPJT is a secondary overvoltage protector for Li-Ion battery packs with 2 to 5 series cells. It monitors each cell voltage and triggers an output when any cell exceeds the factory-programmed threshold. Operating temperature spans -40°C to 110°C, covering the full automotive cabin and most industrial battery enclosures. The upper end leaves margin for self-heating in a sealed pack on a hot day.
The exposed pad is the ground return for the protection FET; a poor solder joint under the pad lifts the thermal impedance and can cause thermal shutdown in fault.