ISL6257

The ISL6257 is a highly integrated battery charger controller for Li-Ion/Li-Ion polymer batteries. ISL6257 is designed for Narrow VDC applications where the system power source is either the battery pack or the regulated output of the charger. This makes the max voltage to the system equal to the max battery voltage instead of the max adapter voltage. Operating at lower system voltage can improve overall efficiency. High efficiency is achieved in the charger with a synchronous buck topology.

The low-side MOSFET emulates a diode at light loads to improve the light load efficiency and prevent system bus boosting. The constant output voltage can be selected for 2, 3 and 4 series Li-Ion cells with ±0.5% accuracy over temperature. It can also be programmed between 4.2V + 5% per cell and 4.2V - 5% per cell to optimize battery capacity. When supplying the load and battery charger simultaneously, the input current limit for the AC adapter is programmable to within ±3% accuracy to avoid overloading the AC adapter and to allow the system to make efficient use of available adapter power for charging. It also has a wide range of programmable charging current. The ISL6257 automatically transitions from regulating current mode to regulating voltage mode.