Electronicdesign 8113 3110col

2 A Buck-Boost Supercapacitor Charger Features Bidirectional Operation

June 2, 2015
Bidirectional, programmable input current buck-boost super capacitor charger, with active charge balancing for 1- or 2-series super capacitors, replaces two separate dc/dc converters (backup regulator and switching charger).

The LTC3110, a bidirectional, programmable input current buck-boost super capacitor charger from Linear Technology, provides active charge balancing for 1- or 2-series super capacitors. Replacing two separate dc/dc converters (backup regulator and switching charger), the device operates in two modes, backup and charge mode.

In backup mode, the charger maintains a system voltage (VSYS) of 1.71 V to 5.25 V, powered from the super capacitor stored energy. The supercap regulator, VCAP, operates from 5.5 V down to 0.1 V, ensuring that all available energy is usable. In charge mode when main power is active, the charger can, autonomously or through user command, reverse the direction of power flow using the regulated system voltage to charge and balance the super capacitors. VCAP is efficiently charged to above or below VSYS by the buck-boost PWM, and a charge-mode average input current limit can be programmed up to 2 A with +/-2% accuracy. Input current limit and maximum capacitor voltage is resistor programmable, and average input current is controlled over a 0.125 A to 2 A programming range. Pin-selectable Burst Mode operation improves light-load efficiency, and reduces standby current to 40 µA and shutdown current to less than 1 µA.

The super capacitor dc/dc regulator is suited for safely charging and protecting large capacitors in backup power applications such as servers and RAID systems, RF systems with battery/capacitor backup. Other applications include small power tools and flashlights, peak load source for vehicle battery systems, and as an energy storage element for regenerative braking systems. The LTC3110 bidirectional buck-boost dc/dc regulator with capacitor charger and balancer is housed in compact, thermally enhanced 24-lead and TSSOP 4 x 4 mm QFN packages, both featuring E- and I-grade operation from 40°C to 125°C, and up to 150°C for the H-grade. Pricing for the E-grade device starts at $4.45 each/1,000.


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