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Diode Array Absorbs High Energy Surges Up To Maximum Junction Temperature

Aug. 2, 2010
Diode array that’s designed to help reduce the size and cost of surge protectors for electronic equipment

Diode array

Geneva, Switzerland: STMicroelectronics has developed a diode array that’s designed to help reduce the size and cost of surge protectors for electronic equipment by providing specified energy absorption capability up to maximum device operating temperature. Current devices must be derated at temperatures above 25°C.

Surge protection is mandatory for most electronic equipment to prevent power-supply fluctuations or electrostatic discharges from damaging sensitive circuitry. A diode array, or transil, is used to divert the surge energy to ground away from the circuitry. Hundreds of millions of these devices are used every year in new products of all types, from handhelds to high-power equipment.

A transil’s energy absorption capability is typically specified at 25°C, dropping to zero at its maximum temperature. Designers often use larger devices to ensure protection over the equipment’s operating range.

According to STMicroelectronics, its SMxJ and SMxT series are the first transils to remedy this limit by maintaining high surge protection all the way to the device’s maximum junction temperature. This allows engineers to use a smaller, lower-cost device with the assurance that adequate protection will be provided. There are six different series in the range, with specified surge energy from 100 to 1500 W (10/1000-µs pulse), covering a broad spectrum of applications.

Additional benefits of the SMxJ and SMxT series include an 80% reduction in leakage current compared to previous generations, which reduces system power consumption and improves energy efficiency. The company also specifies dynamic resistance for its new devices, which allows the clamping voltage to be calculated accurately to improve protection and minimize risk of equipment failure.

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