4A Multi-Cell, Multi-Chemistry Battery Charger Controller from Linear Technology

AC adapter current limiting maximizes the charge rate for a given fixed input power level, allowing the end product to operate at the same time the battery is charging without complex load management algorithms. The IC operates from input voltages up to 28V and is intended for applications including portable computers, portable instruments, and battery backup systems.

The LTC4009's synchronously rectified, buck switching topology drives all n-channel MOSFETs and enables efficiencies as high as 90% at 4A. Final float voltage accuracy is specified at ±0.5% and charge current is programmable with accuracy of ±4%. The LTC4009's quasi-constant frequency PWM architecture guarantees no audible noise operation and minimizes filtering needs, while the high operating frequency of 550kHz allows the use of small inductors and capacitors. Improved non-overlap control keeps efficiency high as external power FET turn on/off times may vary with temperature and supplier. The LTC4009 consumes <20uA in shutdown, increasing battery run time in portable applications. For safety and autonomous charge control, the IC includes battery float voltage over-voltage protection, reverse charge current protection, charge current monitoring, soft start, ac adapter present indication, and current limit indication.