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