KB4540

The KB 4540 is a complete constant-current/constantvoltage linear charger for single cell lithium-ion batteries.
Its ThinSOT package and low external component count make the KB4540 ideally suited for portable applications. Furthermore, the KB4540 is specifically designed to work within USB power specifications.

No external sense resistor is needed, and no blocking diode is required due to the internal MOSFET architecture.

Thermal feedback regulates the charge current to limit the die temperature during high power operation or high ambient temperature. The charge voltage is fixed at 4.2V, and the charge current can be programmed externally with a single resistor. The KB4540 automatically terminates the charge cycle when the charge current drops to 1/10th the programmed value after the final float voltage is reached.

When the input supply (wall adapter or USB supply) is removed, the KB4540 automatically enters a low current state, dropping the battery drain current to less than 2A. The KB4540 can be put into shutdown mode, reducing the supply current to 25A.

Other features include charge current monitor, undervoltage lockout, automatic recharge and a status pin to indicate charge termination and the presence of an input voltage.