Synchronous buck battery charger serves 12 and 24V lead-acid batteries

To charge 12 and 24V lead-acid batteries, Linear Technology has developed the LTC4013, a high voltage, multi-chemistry synchronous step-down battery charger controller.

Input range is from 0 to 60V, and the charger uses temperature-compensated three- and four-stage charge algorithms to efficiently charge batteries. Alternatively, it will charge a multi-cell Lithium-based battery stack with float voltages near to the input supply.

Mode pins define the float voltage and charge algorithm. Charge current is precision regulated to ±5 per cent and programmable with a single resistor up to 20A (depending on the selection of external components). User-adjustable maximum power point tracking (MPPT) circuitry enables simple power optimisation in the case of power-limited sources, such as solar panels. The MPPT open-circuit method corrects for panel temperature changes without the inconvenience of adding a solar panel temperature sensor, adds the company.

Applications include portable medical instruments, monitoring equipment, battery backup systems, industrial handhelds, industrial lighting, military equipment, ruggedised notebooks or tablet computers, plus remote powered communication and telemetry systems.

The charger uses N-channel MOSFETs for charging, with main charging adjusted using pin-strap configurations and programming resistors. The user can select between several pre-defined charging algorithms depending on battery chemistry. For lead-acid battery types such as vented, sealed and gel, the charger supports multiple charging stages, including float, programmable-timed absorption and equaliation. Each charge voltage includes adjustable temperature compensation. For Li-Ion/polymer cells, the device offers a constant-current/constant-voltage charging algorithm. The ‘sync’ input synchronises the switching frequency to an external clock to avoid noise in a particular frequency range or to target noise filters to a specific frequency.

Other product features include an external input MOSFET driver (INFET) to avoid battery discharge during an input supply short, two open-drain status pins, and an ISMON pin that provides analogue information about charge current.

The charger is housed in a compact 28-lead 4.0 x 5.0mm QFN package with an exposed metal pad for excellent thermal performance. E- and I-grade devices are guaranteed for operation from –40 to 125 degree C.

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