Adjustable-Output, Switch-Mode Current Sources with Synchronous Rectifier

High-Accuracy Current Sources Remain Cool While Fast Charging

Please check latest availability status for a specific part variant.


The MAX1640/MAX1641 CMOS, adjustable-output, switch-mode current sources operate from a +5.5V to +26V input, and are ideal for microprocessor-controlled battery chargers. Charging current, maximum output voltage, and pulse-trickle charge are programmed with external resistors. Programming the off-time modifies the switching frequency, suppressing undesirable harmonics in noise-sensitive circuits. The MAX1640's high-side current sensing allows the load to connect directly to ground, eliminating ground-potential errors. The MAX1641 incorporates a low-side current sense.

The MAX1640/MAX1641 step-down pulse-width-modulation (PWM) controllers use an external P-channel MOSFET switch and an optional, external N-channel MOSFET synchronous rectifier for increased efficiency. An internal low-dropout linear regulator provides power for the internal reference and circuitry as well as the gate drive for the N-channel synchronous rectifier.

The MAX1640/MAX1641 are available in space-saving, 16-pin narrow QSOP packages.
MAX1640, MAX1641: Typical Operating Circuit MAX1640, MAX1641: Typical Operating Circuit Enlarge+

Key Features

  • 95% Efficiency
  • +5.5V to +26V Input Supply Range
  • 2V to 24V Adjustable-Output Voltage Range
  • 100% Maximum Duty Cycle (Low Dropout)
  • Up to 500kHz PWM Operation
  • Optional Synchronous Rectifier
  • 16-Pin QSOP Package
  • Current-Sense Accuracy:
    • 2% (MAX1641)
    • 5.3% (MAX1640)


  • Backup Battery Charger
  • Battery-Powered Applications
  • Cell Phones
  • Cordless Phones
  • Handy Terminals
  • Laptop, Notebook, and Palmtop Computers
  • PCS Phones
  • Portable Consumer Products

See parametric specs for Battery Chargers (73)

Part NumberLithium Ion CellsProtected VIN
Charging VIN
Charge Rate Set byCharge TerminationCharge RegulationOper. Temp.
maxmaxSee Notes
2626ResistorExternal ControlSwitchmode-40 to +85
$3.20 @1k

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.

MAX1640EVKIT: Evaluation Kit for the MAX1640, MAX1641
Product Reliability Reports: MAX1640.pdf 
Device   Fab Process   Technology   Sample size   Rejects   FIT at 25°C   FIT at 55°C   Material Composition  

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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