8 A charge current, 2–4 cells — sizing the charging rail
The BQ24705RGERG4 is a multi-chemistry battery charger IC from Texas Instruments, supporting 2 to 4 series cells with a programmable constant-current charge up to 8 A max. That 8 A ceiling sets the charging speed for a multi-cell pack — at 8 A, a 4-cell 4000 mAh pack charges in about 30 minutes from the constant-current phase, but the thermal dissipation in the 24-VFQFN package (4x4 mm exposed pad) demands a solid PCB thermal via array under the pad to keep junction temperature below the 125 °C absolute max. The supply voltage range tops out at 24 V, which covers typical 2- to 4-cell Li-ion packs (8.4 V to 16.8 V nominal) plus headroom for the charger's own dropout. Over-voltage fault protection is built in — if the input rail spikes above the safe limit, the charger shuts down the power FETs without latching, so the pack and the system see no overstress.
Package footprint and thermal planning for the 24-VQFN
The BQ24705RGERG4 ships in a 24-VFQFN Exposed Pad package (4x4 mm body, 0.5 mm pitch). Without that, the 8 A charge current at 12 V input (96 W throughput) will push the die past 125 °C in a 25 °C ambient. The package is Surface Mount, Tape & Reel (TR) — standard for pick-and-place assembly. The 24-VQFN (4x4) footprint is common across TI's BQ2470x family, so a single PCB layout can serve multiple charger variants if the BOM needs a last-minute swap.
Active production — ordering and compliance
The part is RoHS-compliant and halogen-free per TI's standard green packaging.