The RT9538 is a PWM switch mode battery charger controller to fast charge single or multiple Li-ion, NiMH and NiCd batteries, using constant current or constant voltage control. Maximum current can be easily adjusted by an external resistor. The constant voltage output can support up to 30V with 0.5% accuracy.

A third control loop limits the input current drawing from the adapter during charging. This allows simultaneous operation of the equipment and fast battery charging without over loading to the adapter.

The RT9538 can charge batteries from 2.5V to 25V with dropout voltage as low as 2V. A diode is not required in series with the battery because the charger automatically enters a 10μA sleep mode when the adapter is unplugged.

A logic output indicates Li-ion full charge when current drops to 20% of the full-scale adjusted charge current.


  • Notebook Computers
  • Portable Instruments
  • Chargers for Li-ion, NiMH, NiCd and Lead Acid
  • Rechargeable Batteries
Key Spec.
Status NRND
Vin (min) (V) 4.5
Vin (max) (V) 28
Battery Charge Voltage (max) (V) 25
Status Indicator Yes
Charger Type Switching
Input Source AC Adapter
Features Current Mode Control;Enable Input;OCP;OVP;SCP;UVP
Package Type WQFN4x4-16
Built-in Power MOSFETs No
  • Fast Charging for Li-ion, NiMH and NiCd Batteries
  • Adjustable Battery Voltages from 2.5V to 25V
  • High Efficiency : Up to 95%
  • Charging Current Adjusted by Resistor
  • Precision 0.5% Charging Voltage Accuracy
  • Provide 5% Charging Current Accuracy
  • Input Current Limit Maximizes Charging Rate
  • 475kHz Switching Frequency
  • Flag Indicates Li-ion Charge Completion
  • Auto Shutdown with Adapter Removal
  • Only 10μA Battery Drain When Idle
  • Available in an 16-Lead WQFN Package
  • RoHS Compliant and Halogen Free
TitleLast UpdateDownload
High Efficiency Switching Mode Battery Charger2013/11/04
Additional Documents
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Power Management Components for Lithium-Ion Battery Powered Applications