Analog Devices MAX745 Product Info

• 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

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%.

For a similar device with an SMBus™ microcontroller interface and the ability to charge NiCd and NiMH cells, refer to the MAX1647 and MAX1648. For a low-cost Li+ charger using a linear-regulator control scheme, refer to the MAX846A.

Applications

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