Single-cell Li-ion linear charger in a PowerPAD package
The Texas Instruments BQ24003PWP is a linear battery charger IC designed for single-cell Lithium Ion packs. The device integrates over-temperature fault protection and offers programmable charge current and timer settings. This is a linear topology charger — the pass element drops the difference between the input supply and the battery voltage as heat.
The 1.2 A max charge current sets the charge time for a given cell capacity — a 2400 mAh pack charges in roughly two hours at this rate, minus the constant-voltage taper. The 4.2 V termination voltage is the standard full-charge threshold for Li-ion cells with a graphite anode. The charger holds the battery at this voltage during the constant-voltage phase until the current tapers to the programmed termination threshold. Programmable current and timer features let the designer set the charge rate and safety timeout via external resistors. The over-temperature fault protection shuts down the charger if the die temperature exceeds the internal threshold — this is a thermal foldback, not a system-level cutoff, so the PCB thermal design still sets the sustained charge rate.