The ISL6251, ISL6251A is a highly integrated battery charger controller for Li-Ion/Li-Ion polymer batteries and NiMH batteries. High Efficiency is achieved by a synchronous buck topology and the use of a MOSFET, instead of a diode, for selecting power from the adapter or battery. The low side MOSFET emulates a diode at light loads to improve the light load efficiency and prevent system bus boosting.