2-to-7-cell Li-ion guard with SMBus telemetry
The BQ40Z80RSMT is a multi-function controller from Texas Instruments purpose-built for Lithium Ion and Lithium Polymer battery packs spanning 2 to 7 series cells. It communicates over an SMBus interface, so the host system reads state-of-charge, voltage, and fault flags directly without an external ADC or gauge chip.
Fault protection scope — what each monitor catches
The device integrates protection against overcurrent, overtemperature, overvoltage, undervoltage, and short circuit. Overcurrent detection prevents the pack from sourcing into a dead short or an excessive load that would stress the cells; the overtemperature monitor shuts down charge or discharge when the internal or external thermistor trips; over/under voltage per-cell protection keeps each series element inside its safe window. This is a single-chip safety supervisor, not just a coulomb counter.
32-VQFN package — thermal and layout notes
The part is housed in a 32-VFQFN exposed pad (4x4 mm, supplier package 32-VQFN). Surface-mount assembly with the pad tied to the ground pour keeps the junction temperature within the -40 to 85°C operating range during charge/discharge transitions.