Low Cost Multi-Chemistry Battery Charger Controller

Product Status: Mass Production


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.

The constant output voltage can be selected for 2, 3 and 4 series Li-Ion cells with 0.5% accuracy over-temperature. It can be also programmed between 4.2V+5%/cell and 4.2V-5%/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 ISL6251, ISL6251A provides outputs that are used to monitor the current drawn from the AC adapter, and monitor for the presence of an AC adapter. The ISL6251, ISL6251A automatically transitions from regulating current mode to regulating voltage mode.


  • ±0.5% Charge Voltage Accuracy (-10°C to +100°C)
  • ±3% Accurate Input Current Limit
  • ±3% Accurate Battery Charge Current Limit
  • ±25% Accurate Battery Trickle Charge Current Limit (ISL6251A)
  • Programmable Charge Current Limit, Adapter Current Limit and Charge Voltage
  • Fixed 300kHz PWM Synchronous Buck Controller with Diode Emulation at Light Load
  • Output for Current Drawn from AC Adapter
  • AC Adapter Present Indicator
  • Fast Input Current Limit Response
  • Input Voltage Range 7V to 25V
  • Supports 2, 3 and 4 Cells Battery Pack
  • Up to 17.64V Battery-Voltage Set Point
  • Thermal Shutdown
  • Support Pulse Charging
  • Less than 10µA Battery Leakage Current
  • Charge Any Battery Chemistry: Li-Ion, NiCd, NiMH, etc.
  • Pb-Free (RoHS Compliant)


 Block Diagram


Basic Information
Production Status
Mass Production
Input Voltage Min (V)
Input Voltage Max (V)
Input Current Limit Accuracy (%)
Battery Charge Voltage (V)
4.2/Cell (2S, 3S, 4S)
Charging Voltage Accuracy Max (%)
Battery Charge Voltage Adjust (%)
Charge Current Limit Accuracy (%)
±5 (CHLIM=2.0V)
Trickle Charge Current Limit Accuracy (%)
±50 (CHLIM=0.2V)
Automatic Trickle Charge Typ (V)
No (Set by Host)
Battery Leakage Current Max (μA)
10 (DCIN=0V, No System Load)
Automatic Power Source Selection
DC Adapter Detection
Fixed Frequency Synchronous Buck
Switching Frequency Typ (kHz)
Max Duty Cycle (%)
Audible Noise
Thermal Shutdown (°C)
150 °C
Battery Chemistry
Multi-Cell Li+/Polymer
Qualification Level
Input Voltage Range (V)
7 to 25
Can Sample
Temperature Range
-10 to +100

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