Single-cell Li-ion charger in a 3×3 VSON
The Texas Instruments BQ24081DRCRG4 is a linear battery charger IC designed for single-cell Lithium Ion or Lithium Polymer packs. It delivers a regulated 4.2V charge voltage and supports a programmable charge current up to 1A. The device is built for constant-current / constant-voltage (CC/CV) charging with programmable current and timer settings, giving the designer control over the charge profile without external passives. Housed in a 10-pin VSON package with an exposed thermal pad (3×3 mm), it suits space-constrained portable designs where thermal dissipation from the linear regulator matters.
The 4.2V battery voltage is the standard termination voltage for most single-cell Li-ion and Li-Po cells. The 1A maximum charge current sets the thermal ceiling — in a linear charger, the power dissipated as heat equals (VIN - VBAT) × ICHG, so a 5V input at 1A into a 3.7V cell dissipates 1.3W. The programmable timer prevents overcharging if the termination current threshold is never reached — a safety net for cells with high internal impedance or when the input supply is marginal.
The linear topology means the die temperature tracks the ambient plus the self-heating from the charge current.