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
