LT unveils battery charger controller

Linear Technology has introduced the LTC4009, a 4A switchmode battery charger controller for multiple battery chemistries, which minimises power dissipation without compromising board space.

The LTC4009 supports Li-Ion/Polymer, NiMH, NiCd and sealed lead acid battery chemistries in multi-cell configurations.

AC adaptor current limiting maximises 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 gives efficiencies as high as 90 per cent at 4A.

Final float voltage accuracy is specified at +/-0.5 per cent, and charge current is programmable with accuracy of +/-4 per cent.

The LTC4009's quasi-constant frequency PWM architecture guarantees no audible noise operation and minimises 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 less than 20 microamps in shutdown, increasing battery runtime 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 adaptor present indication and current limit indication.

The LTC4009 is housed in a compact 20-lead, low-profile (0.75mm) 4mm x 4mm QFN package.

It is guaranteed for operation from 0 to 85C ambient temperature.

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