2-cell Li-Ion charger at 8.4V, 1.2A ceiling
The Texas Instruments BQ24005PWPG4 is a linear Li-Ion charger IC designed specifically for 2-cell battery packs, charging to a nominal 8.4V pack voltage. It delivers a constant charge current programmable up to 1.2A maximum, with a separate timer and current-programming pin for tailoring the charge profile. Over-temperature fault protection is built in, and the operating temperature range covers -40°C to 70°C — suitable for portable equipment, medical handhelds, and industrial instrumentation that lives indoors or in a conditioned enclosure.
Charge profile and programmability
The charger uses a constant-current / constant-voltage algorithm. The charge current is set by an external resistor on the ISET pin, and the safety timer is programmed via a capacitor on the TIMER pin. This gives the designer control over the charge rate and termination time without firmware intervention — useful for a standalone charger that must not overcharge a 2-cell pack if the battery voltage never reaches the regulation threshold.
Supply rail and thermal envelope
The maximum supply voltage is 10V, so a 5V USB supply or a 9V wall adapter works directly; a 12V rail needs a preregulator to stay under the 10V ceiling.