Part overview — what the BQ771807DPJR does on a Li-ion pack
The Texas Instruments BQ771807DPJR is a dedicated battery protection IC for lithium-ion packs built from 2 to 5 series cells. It monitors each cell voltage and triggers a fault output when any cell exceeds the over-voltage threshold — a single-purpose protector, not a full fuel gauge or secondary protector with over-current or over-temperature detection. The part comes in an 8-WSON (3x4) package with an exposed pad for thermal relief, and operates over a -40°C to 110°C range that covers the internal environment of a sealed battery pack.
What the ratings mean for the BOM
The 2-5 cell range is the headline selection parameter: this IC fits a 2S to 5S Li-ion pack. If your BOM calls for a 1S or 6S+ protector, this part does not fit — the BQ79612PAPRQ1 covers single-cell automotive applications. The over-voltage-only fault protection means the designer must add separate over-current (fuse, PTC, or current-sense supervisor) and over-temperature (NTC + comparator) protection externally. The -40°C to 110°C operating range is wide enough for most portable and light industrial packs, but a hot engine-bay or downhole application would exceed the 110°C ceiling.
Package and mounting — what to expect on the board
The 8-WSON (3x4) package with exposed pad is a small, leadless DFN. The exposed pad must be soldered to a PCB thermal land and connected to the ground plane for heat sinking. Stencil aperture design for the pad is critical — too little solder and the part lifts during reflow; too much and the pad floats. Tape & Reel (TR) and Cut Tape (CT) options are available, so the part can be ordered in production reels or small quantities for prototyping.