IC Manages NiMH Coin Cell Charging/Backup January 2007 Issue Published Date: December 06, 2006
The MAX8672 backup-battery management IC provides complete charging and backup switchover control for enterprise PDAs and other smart portable devices. The device charges 1- or 2-cell NiMH coin-cell batteries and features a programmable charge current, termination voltage, and charge timer. To optimize charge time and maximize cell life, the charge algorithm allows standard fast-charge, trickle-charge, and deep-recovery-charge modes. Protective features include an integrated thermistor sensor that disables fast-charging when the temperature exceeds the safe operating range and a battery-restart-charge threshold to prevent overcharging. The IC also manages backup switchover from a primary power source. An accurate, on-chip voltage detector monitors the main supply and backs up two system supplies (typically I/O and memory) when the main power source falls below the preset voltage. The backup cells are stepped up by an on-chip, synchronous-rectified, low-quiescent-current boost converter. A low-quiescent-current LDO generates a second backup voltage. Additionally, the device does not require external diodes or FETs to prevent reverse currents on the backup-battery, boost, and LDO pins. Available in a 3 mm x 3 mm, 14-pin TDFN package and specified for the extended temperature range (-40°C to 85°C), pricing starts at $1.87 each/1,000. An evaluation kit is available to speed designs. MAXIM INTEGRATED PRODUCTS, Sunnyvale, CA. (800) 998-8800.
