The MAX745 provides all functions necessary for charging lithium-ion 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 4.0V and 4.4V using standard 1% resistors, and then the number of cells is set from 1 to 4 by pinstrapping. Total output voltage error is less than 0.75%. For a similar device with an SMBusTM microcontroller interface and the ability to charge NiCd and NiMH cells, refer to the MAX1647 and MAX1648. For a low-cost lithium-ion charger using a linear-regulator control scheme, refer to the MAX846A.