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STMicroelectronics has announced an innovation that will help reduce the size and cost of surge protectors for electronic equipment by providing specified energy absorption capability up to the maximum operating temperature. Competing devices must be derated significantly 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 commonly 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 usually specified at 25°C, reducing to zero at its maximum temperature. Designers often use larger devices to ensure protection over the equipment’s operating range.

ST’s new SMxJ and SMxT series Transils are the first to remedy this 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 100W to 1500W (10/1000-microsecond pulse) thereby covering a broad spectrum of applications.

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

Major features of SM series include: High surge capability at maximum junction temperature; ESD protection meeting IEC 61000-4-2 and MIL-STD-883G; Specified with 8/20µs surge to meet IEC 61000-4-5 for electrical over-stress Leakage current specified at 85°C, meeting telecommunication industry requirements; Operating temperature range: -40°C to 150°C enabling use in consumer, telecom and industrial applications.


ST Microelectronics