MAX745 Switch-Mode Lithium-Ion Battery-Charger

Description
The MAX745 provides all functions necessary for charging lithium-ion (Li+) battery packs. It provides a regulated charging current of up to 4A without getting hot, and a regulated voltage with only ±0.75% total error at the battery terminals. It uses low-cost, 1% resistors to set the output voltage, and a low-cost N-channel MOSFET as the power switch.

The MAX745 regulates the voltage set point and charging current using two loops that work together to transition smoothly between voltage and current regulation. The per-cell battery voltage regulation limit is set between 4V and 4.4V using standard 1% resistors, and then the number of cells is set from 1 to 4 by pin-strapping. Total output voltage error is less than ±0.75%.

Key Features

    Charges 1 to 4 Li+ Battery Cells
    ±0.75% Voltage-Regulation Accuracy Using 1% Resistors
    Provides up to 4A without Excessive Heating
    90% Efficient
    Uses Low-Cost Set Resistors and N-Channel Switch
    Up to 24V Input
    Up to 18V Maximum Battery Voltage
    300kHz Pulse-Width Modulated (PWM) Operation Low-Noise, Small Components
    Stand-Alone Operation—No Microcontroller Needed

Applications/Uses

    Cell Phones
    Desktop Cradle Chargers
    Handheld Instruments (PDAs, Palmtops)
    Li+ Battery Packs
    Notebook Computers