ISL9201 pdf datasheet (Li-ion

The ISL9201 is an integrated single-cell Li-ion or Li-polymer
charger capable of operating at an input voltage as low as
2.5V. The low operating voltage allows the charger to work
with a variety of AC adapters.
The ISL9201 operates as a linear charger when the AC
adapter is a voltage source. The battery is charged in a
standard Li-ion charge profile, i.e. a constant current phase
followed be a constant voltage phase (CC/CV). The charge
current during the constant current phase is determined by the
external resistor connected to the IREF pin. When the adapter
output is a current-limited voltage source and the current limit
is smaller than the programmed constant current of the IC, the
ISL9201 operates as a pulse charger where the charge
current is determined by the current limit of the AC adapter
during the constant current phase. The ISL9201 operates in a
linear mode during the constant voltage phase in both adapter
cases.