Advanced Chemistry-Independent, Level 2 Battery Charger with Input Current Limiting

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The MAX1645B is a high-efficiency battery charger capable of charging batteries of any chemistry type. It uses the Intel System Management Bus (SMBus) to control voltage and current-charge outputs.

When charging lithium-ion (Li+) batteries, the MAX1645B automatically transitions from regulating current to regulating voltage. The MAX1645B can also limit line input current so as not to exceed a predetermined current drawn from the DC source. A 175s charge safety timer prevents "runaway charging" should the MAX1645B stop receiving charging voltage/current commands.

The MAX1645B employs a next-generation synchronous buck control circuitry that lowers the minimum input-to-output voltage drop by allowing the duty cycle to exceed 99%. The MAX1645B can easily charge one to four series Li+ cells.
MAX1645B: Typical Operating Circuit MAX1645B: Typical Operating Circuit Enlarge+

Key Features

  • Input Current Limiting
  • 175s Charge Safety Timeout
  • 128mA Wake-Up Charge
  • Charges Any Chemistry Battery: Li+, NiCd, NiMH, Lead Acid, etc.
  • Intel SMBus 2-Wire Serial Interface
  • Compliant with Level 2 Smart Battery Charger Spec Rev 1.0
  • +8V to +28V Input Voltage Range
  • Up to 18.4V Battery Voltage
  • 11-Bit Battery Voltage Setting
  • ±0.8% Output Voltage Accuracy with Internal Reference
  • 3A (max) Battery Charge Current
  • 6-Bit Charge-Current Setting
  • 99.99% (max) Duty Cycle for Low-Dropout Operation
  • Load/Source Switchover Drivers
  • >97% Efficiency


  • Notebook Computers
  • Personal Digital Assistants
  • Point-of-Sale Terminals
Part NumberLithium Ion CellsProtected VIN
Charging VIN
Charge Rate Set byMax. ICHG
Charge TerminationCharge RegulationOper. Temp.
3Smart Battery ControlSwitchmode-40 to +85
See All Battery Chargers (75)
Pricing Notes:
This pricing is BUDGETARY, for comparing similar parts. Prices are in U.S. dollars and subject to change. Quantity pricing may vary substantially and international prices may differ due to local duties, taxes, fees, and exchange rates. For volume-specific and version-specific prices and delivery, please see the price and availability page or contact an authorized distributor.

MAX1645BEVKIT: Evaluation Kit/Evaluation System for the MAX1645B
MAX1645BEVSYS: Evaluation Kit/Evaluation System for the MAX1645B

Quality and Environmental Data

Request Reliability Report for: MAX1645B 
Lead-Free Package Tin (Sn) Whisker Reports

CAD Symbols and Footprints

  • MAX1645BEEI
  • MAX1645BEEI+
  • MAX1645BEEI+T
  • MAX1645BEEI-T
  • Device   Fab Process   Technology   Sample size   Rejects   FIT at 25°C   FIT at 55°C  

    Note : The failure rates are summarized by technology and mapped to the associated material part numbers. The failure rates are highly dependent on the number of units tested.

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