Ultra-miniature Transil family from delivers 400W suppression capability

STMicroelectronics has introduced the SMM4F family of unidirectional Transil voltage surge-suppression diodes, which improves performance in three key areas by delivering high protection within a small footprint, reducing leakage current for low losses, and raising maximum junction temperature for enhanced reliability.

The SMM4F family protects against 400W 10/1000 microsecond surges and has an ultra-compact footprint of 3.8 x 1.9mm. Smaller than existing 400W devices in SMA packages, the SMM4F diodes also provide 100% more protection than 200W alternatives currently offered in the 10% smaller SMF outline. Low leakage current of 0.2 microamps ensures low-loss performance for use in battery-operated devices or other low-power applications. With a maximum leakage current of 1 microamp at 85 degrees C, the SMM4F family is suitable for telecom applications.

The family includes a total of 14 devices with stand-off voltages between 5V and 33V providing a suitable part for the majority of applications requiring surge suppression diodes, including SMPS, consumer electronics, computing devices and telecom equipment. Each is rated to 175 degrees C maximum junction temperature, allowing a greater safety margin than conventional alternatives that are typically rated to only 150 degrees C.

ST has also characterized additional parameters, providing designers with reliable data to predict behavior accurately under a variety of operating conditions. The maximum clamping voltage and peak-power current are specified for surges of 8/20 microseconds in addition to 10/1000 microseconds, allowing designers to verify protection meeting the widely accepted IEC61000-4-5 standard. Designers also benefit from accurate data for dynamic resistance, variation of breakdown voltage with temperature, and leakage current versus junction temperature. ST is the only manufacturer to provide this information, which allows designers to calculate the clamping voltage accurately, according to actual surge-current and junction-temperature values.

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