Batteries and Portable Power

3A Buck-Boost Super Capacitor Charger with Active Capacitor Balancing

Linear Technology Corporation introduces the LTC3128, a high efficiency, input current-limited buck-boost super capacitor charger with active charge balancing for 1 or 2 series super capacitors. The LTC3128 features an average input current limit that can be programmed up to 3A with +/-2% accuracy, preventing power source overload while minimizing capacitor recharge time. Highly efficient active charge balancing eliminates dissipative external ballast resistors, ensuring balanced operation and charging with mismatched capacitors, and less frequent recharge cycles. A programmable maximum capacitor voltage clamp actively monitors and enforces the voltage across each capacitor in the series stack, ensuring reliable operation as capacitors age and develop mismatched capacities.

The low noise buck-boost topology allows the output super capacitor to be charged whether above or below the input. The low-RDS(on), low gate charge synchronous switches provide high efficiency conversion to minimize the charging time of storage elements. This combination of features makes the LTC3128 suited for safely charging and protecting large capacitors in backup power applications.

The LTC3128's input current limit and maximum capacitor voltage are each programmed using a single resistor. Average input current is accurately controlled over a 0.5A to 3A programming range, and the individual maximum capacitor voltage can be set from 1.6V to 3.0V. Other features of the LTC3128 include <1µA quiescent current from VOUT in Burst Mode® operation, accurate power good and power failure indicators, and thermal overload protection.

The LTC3128 is housed in compact, thermally enhanced 4mm x 5mm QFN and 24-lead TSSOP packages, both featuring operation from -40 to 125 degrees C. Pricing for the E-grade device starts at $3.95 each in 1,000-piece quantities.

Linear Technology Corporation
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