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High efficiency transformer driver suits smart grid applications

Maxim Integrated Products announces the MAX13256, an H-bridge transformer driver featuring a wide input-voltage range for isolated power supplies. Using this simple component, engineers can easily design a highly efficient (up to 90%) isolated dc-dc converter.

Here's how it works: The MAX13256 drives a transformer’s primary coil with up to 300 mA of current from an 8 to 36 Vdc supply, which can deliver up to 10 W of isolated power. Users can choose their own transformer winding ratio, which defines the output voltage, thereby allowing the selection of virtually any isolated output voltage. This extensive supply range eliminates external voltage regulation, while integrated protection features prevent system-level failures. By eliminating 16 discrete components, the MAX13256 simplifies BOM complexity and reduces footprint with high integration in a tiny TDFN package. With these capabilities, the MAX13256 driver is a simple way to create isolated power supplies in smart grid metering applications, as well as in medical and industrial equipment.

Smart grid applications that use wired interface communications require isolated power to protect against high-voltage mains that can damage both the installer and power meter’s internal electronics. The isolated power is typically generated with a transformer and discrete components, which increase system size and add cost. The MAX13256 drives the transformer that acts as the additional form of isolation from high-voltage mains.

A smart grid has different requirements for input voltage and output power that vary based on the type of interface used to communicate with the smart meter. The MAX13256’s wide 8 to 36 V input voltage range addresses these diverse power-supply input requirements. It also eliminates external voltage regulation, and enables flexible transformer options to satisfy a range of power output requirements.

The MAX13256 also integrates protection features that prevent system-level failures. Adjustable current limiting allows indirect limiting of secondary-side load currents. An overcurrent limit is set by an external resistor over the 215 to 650 mA range. An active-low FAULT output alerts users when the device detects an overtemperature or overcurrent condition. This integrated thermal and short-circuit protection ensures safe operation and reduces both cost and PCB space over discrete solutions.

Highly integrated H-bridge and transformer modules are typically more expensive solutions that are limited to providing users with system-optimized isolated output voltages. For applications requiring a simple low-cost approach for nonregulated dc-dc isolation, the MAX13256 is a suitable fit.

The high efficiency of the MAX13256 (up to 90%) helps reduce heat in applications where space is at a premium. In addition, the device features a low-power mode to reduce the overall supply current to 0.65 mA when the driver is not in use.

The MAX13256 is available in a 10-pin TDFN package and is specified over the -40° to 125° C automotive temperature range.

For more information, contact Maxim Integrated Products, 120 San Gabriel Dr., Sunnyvale, CA 94086. Phone: (408) 737-7600.

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