June 5, 2012 – Linear Technology Korea (CEO Hong Sa-gwak) announced the development of the LTC4370, the company's first current-sharing controller with reverse current blocking functionality. The LTC4370 breaks away from the limited and complex conventional current-sharing methods, providing a simpler, faster, and more space-efficient solution for sharing between two supplies. The ability to work regardless of supply type makes designs more flexible and extends system lifetime. By incorporating diode operation, this controller prevents the entire system from shutting down due to a single supply failure.
High-availability system designers implement redundancy in power systems by connecting two similar supplies with integrated diodes (diode-OR) in parallel, so that if one fails, the other can handle the load. System reliability increases when both supplies operate simultaneously and each shares the load current equally. With low-current operating characteristics, the operating temperature is slightly lower, reducing failure rates by half for every 10°C temperature reduction. Additional benefits of load sharing include faster recovery time after a supply failure and the ability to operate supplies near the peak efficiency point. Prior to the LTC4370, load-sharing solutions required active control of supplies through trim pins or feedback networks. Additionally, stability compensation was needed depending on supply type along with a shared bus. The LTC4370 significantly simplifies the design of reliable power systems.
The LTC4370 controls N-channel MOSFETs connected in series with each supply. These MOSFETs function like diodes with variable forward voltage. The LTC4370 adjusts the forward voltage of the MOSFET diodes to offset mismatches in input supply voltage until the current from each supply becomes equal. To limit MOSFET power dissipation, the maximum voltage drop across the MOSFET can be adjusted with external resistors. This controller operates with supplies in the 0V to 18V range. In case of failure, fast MOSFET turn-on/turn-off limits load voltage sag and inrush current between supplies. The enable pin can turn off each MOSFET, and when both are off, the controller bias current decreases. A status pin indicates the state of the MOSFET, which can be used to signal that current sharing is temporarily suspended by illuminating a red LED. Load-sharing functionality can also be disabled to use the device as a dual ideal-diode controller.
Across the full commercial and industrial temperature range, the LTC4370 is available in 16-pin DFN (4mm x 3mm) and MSOP packages. Pricing is $4.95 per unit based on quantities of 1,000 units, and it is currently supplied for volume production. Evaluation circuit boards are also available for purchase online or through regional sales offices. For detailed product information, refer to www.linear.com/product/LTC4370.

Photo caption: Current-sharing IC improves system reliability without supply trimming

LTC4370 Product Features

• Load sharing between two supplies
• Eliminates the need for active control of input supplies
• No shared bus required
• Reverse current blocking
• No inrush current at startup or during faults
• 0V to 18V operation
• Enable input
• MOSFET status output
• Dual ideal diode mode
• 16-pin DFN (4mm x 3mm) & MSOP package