Use transient voltage suppression diodes to ruggedize circuits and maintain electrical integrity
parameters cannot satisfy all EFT situations. Examples from four distinct families illustrate these points. 1) The SMFE series has a peak pulse power capability of 200 watts with a 10/1000 µs waveform. The devices are housed in an industry- standard low-profile SOD-123FL surface-mount package measuring 2 × 3 × 1.35 millimeters (mm) that optimizes board space for mobile and wearable devices. One member of the series is the SMFE5-0A (Figure 9). It has a 9.2 V clamping voltage, a 21.7 ampere (A) I pp , and supports unidirectional or bidirectional use cases. Reverse leakage current is under 1 μA above 10 V operation, and the response time is fast, typically less than 1.0 picosecond (ps) from 0 volts to V BR . 2) The ST series protects one bidirectional I/O line, and targets USB and other data ports, touchpads, buttons, DC power, RJ-45 connectors, and RF antennas. Members of this family such as the 33 volt, 12 A I pp STS321120B301 are housed in a tiny SOD-323 SMT package measuring 1.8 × 1.4 × 1.0 mm and are rated to 400 watts peak pulse power per line (tP = 8/20 μs). Diodes in this series support working voltages spanning 2.8 volts DC (V DC ) to 70 V DC with ultra- low capacitance down to 0.15 pF. These diodes provide ESD protection up to 30 kV (per IEC 61000-4-2).
3) The AK series comprises high-power TVS diodes with up to 10,000 A protection and is designed to meet severe surge- test environments for AC and DC applications. These diodes feature low slope resistance as well as a superior clamping factor due to snapback technology. They meet UL1449 surge-protection device standards for applications such as consumer electronics, appliances, industrial automation, or AC line protection. (Note: slope or dynamic resistance is the resistance offered by the diode when an AC voltage is applied; snapback is a device process whereby conduction of large currents continues even at lower voltages.)
To meet the amperage and UL requirements, devices in this series use through-hole axial- lead packaging as used with the AK6E-066C, a 120 V clamp, and 6000 A I pp diode (Figure 10). This diode measures 25 mm along its leads, with a nearly square “central” body that measures approximately 13 × 15 mm.
Figure 10: The AK6E-066C high- power 120 V TVS diode offers up to 10,000 A protection and is housed in a through-hole axial-lead package. (Image source: Eaton) 4) The SMAJExxH series SMA- size TVS diodes are unique in that they are qualified to AEC-Q101 standards required for automotive applications. They provide 400 watt peak pulse power capability (with a 10/1000 μs waveform) and have a fast response time that is typically less than 1.0 ps from 0 V to V BR , along with I R less than under 1 μA above 10 volts.
Figure 9: The SMFE5-0A 9.2 V TVS diode comes in a low-profile SOD-123FL surface-mount package and targets mobile and wearable applications. (Image source: Eaton)
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