Power Electronics

Isolated Power, 36V, H-Bridge Transformer Driver

Maxim Integrated Products introduces the MAX13256, an H-bridge transformer driver with a wide input-voltage range for isolated power supplies. Using this simple solution, engineers can quickly design a highly efficient (up to 90%) isolated DC-DC converter.

The MAX13256 drives a transformer's primary coil with up to 300mA of current from an 8V to 36V DC supply which can deliver up to 10W of isolated power. Users can choose their own transformer winding ratio which defines the output voltage, thus allowing the selection of virtually any isolated output voltage. This robust supply range eliminates external voltage regulation. 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 all these capabilities, the MAX13256 driver is a simple way to create isolated power supplies in smart grid metering applications, and industrial and medical equipment.

Smart grid applications utilizing 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 the solution 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 8V to 36V input voltage range addresses these diverse power-supply input requirements. It also eliminates external voltage regulation, and enables flexible transformer options to satisfy a wide 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 215mA to 650mA (typ) range. An active-low FAULT output asserts 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 customers with system optimized isolated output voltages. For applications requiring a simple low-cost approach for non-regulated DC-DC isolation, the MAX13256 is an ideal fit.

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

The MAX13256 is available in a 10-pin TDFN and is specified over the -40 degrees Celsius to +125 degrees Celsius automotive temperature range. Pricing starts at $2.85 (1000-up). An evaluation (EV) kit is also available.

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