General Description

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.

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)

Applications

Battery-Powered Equipment

Laptop, Notebook, and Palmtop Computers

Handy Terminals

Portable Consumer Products

Cordless Phones

Cellular Phones

PCS Phones

Backup Battery Charger