New from Linear Technology is the LTC4370, a current-sharing controller with reverse current blocking. According to the manufacturer, it frees the designer from the limitations and complications of existing current-sharing methods to obtain a simpler, quicker and space-saving solution for sharing between two supplies.
The IC’s supply-agnostic feature lends flexibility and a longer lifetime. By incorporating diode behaviour, the controller prevents one supply failure from bringing down the entire system.
Designers of high-availability systems frequently engineer redundancy into their power systems by paralleling two similar supplies with diodes (diode-OR) such that one can handle the load when the other fails. System reliability is further increased if both supplies operate simultaneously, each sharing half the load current. Lower currents lead to cooler operation, reducing the failure rate by half for every 10°C fall in temperature.
Other load-sharing benefits include faster recovery after supply failure, and the ability to operate supplies near their peak efficiency point. Without the LTC4370, load-sharing solutions demand active control of the supplies through their trim pins or feedback networks. They also required a share bus, and stability compensation dependent on the supply type.
The LTC4370 controls N-channel MOSFETs in series with each supply. These MOSFETs act like diodes with a variable forward voltage. The chip adjusts the forward voltage of the MOSFET diodes to offset the mismatch in input supply voltages until the currents from each supply are equal.
To limit MOSFET power dissipation, the maximum voltage drop across the MOSFET is adjustable with an external resistor. The controller operates with supplies in the range of 0 V to 18 V. During faults, fast MOSFET turn-on and turn-off limit the load voltage droop and shoot-through currents between supplies.
Enable pins can turn each MOSFET off; when both are off, the controller bias current is lowered. Status pins indicate the MOSFET on-state, which can be used to signal a break in current sharing. The load sharing feature can also be switched off to turn the device into a dual ideal-diode controller.
Specified over the full commercial and industrial temperature ranges, the LTC4370 is offered in 16-pin DFN (4 mm x 3 mm) and MSOP packages. Evaluation circuit boards are available.
For more information contact Kevin Godfrey, Arrow Altech Distribution, +27 (0)11 923 9600, [email protected], www.arrow.altech.co.za
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