Electronic Design

Enhanced Trench Structure Yields Better MOSFETs

Datel teamed up with Cisco to develop a dc-dc converter to power the Cisco 3200 Mobile Access Router, which enables transmission of data, voice, and video over wireless networks. Compliant with PC/104-plus specifications, the MAPC-104 is a nonisolated, triple-output dc-dc converter designed to deliver its rated 46-W output under harsh environmental conditions. Using an internal analog-to-digital converter and microcontroller, the device implements a number of advanced monitoring and control functions.

The MAPC-104 converts a vehicle's standard battery voltage of 12 or 24 V to three fully regulated outputs capable of 3.3 V at 6 A, 5.1 V at 6.3 A, and 12 V at 100 mA. Total output power is restricted to 46 W. Using synchronous rectification in a buck/boost topology, the converter achieves efficiencies up to 92.5%. This enables full-power operation up to as high as 85°C with a mere 100 LFM of airflow. In addition, the supply withstands high input transient voltages in accordance with SAE J1455 and J1211.

An internal microcontroller allows the converter to set three thresholds of overtemperature protection. The converter is rated for operation at board temperatures of −40°C to 105°C. At a board temperature of 115°C, the converter issues a warning for 30 seconds before shutting down. It sets a hysteretic threshold at 110°C. When the temperature drops down to this level, the converter will restart. When the board temperature reaches 125°C, the converter shuts down immediately. These thresholds are set in software, so they may be modified if necessary.

Datel Ltd.

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