Tvs Diode Array Spa Diodes Page 10 TVS Diode Array SPA Diodes Catalog

2017 Littelfuse, Inc. Specifications are subject to change without notice. Revised: 02/23/17 TVS Diode Arrays (SPA Diodes) ESD Electrical Characteristics ESD, in contrast to switching and surge transients, has a very short transition from zero to maximum current and voltage. The rise time of an ESD event is less than 1 nanosecond (1ns), while the other transients take longer than 1 microsecond (1s) to reach their peaks. The International Electrotechnical Commission (IEC) has developed a model of an ESD event for the user environment. The model defined in the IEC61000-4-2 standard is used for determining if systems (computers, networks, cell phones, set top boxes, etc.) are susceptible to ESD events. The test specification quantifies the methodology for introducing ESD into the system as well as the various voltage and current levels that define the ESD event. Internal circuits or ICs have some level of ESD protection "on chip"; however, they are almost always much less than the typical ESD levels seen in the field. Furthermore, the internal ICs are commonly evaluated using a manufacturing environment test standard (MIL-STD-883, Method 3015) that generates voltages and current levels far below that of the IEC "system level" standard. The current levels can differ by more than 100 fold, and more about this is discussed on page 13 in the section titled "ESD Immunity Test Standards" . ESD Damage Risks A transient discharged into an electronic system creates three general types of adverse effects: 1. Soft Failures/Data Corruption: can occur to a part of the data stream, or the system may latch up. This is a temporary problem and is solved by data correction (for data corruption) or by re-booting the system (for latch up). 2. Latent Defects: A component might be partially degraded, but able to function properly. Typically a latent defect may cause a system to fail prematurely. 3. Catastrophic Failures: An internal component is rendered inoperable, and cannot function properly. This is a permanent condition. In the case of Junction Burnout , a short circuit condition is created in a transistor of the circuit. The metallic interconnect (Trace Line) is "pulled through" one of the semiconductor layers (Alloy Spike) or one of the semi conducting junctions is directly short circuited (Junction Short). In Oxide Punch-Through , the metallic interconnect is "pulled through" the oxide layer to provide a short circuit on the signal line. In Metallization Burnout , the metallic interconnect is melted, much like a fuse. It creates an open circuit condition on the signal line. The use of ESD circuit protection components like Littelfuse SPA Diodes will help you avoid such problems. Why Implement Circuit Protection? It is important to consider that most electronic equipment will spend 99% of its useful life in environments where it is subject to ESD. ESD can be generated from a wide range of everyday factors such as very dry air, static from plastics, or walking across a floor or carpet, and can be present during every phase of useful life from manufacturing, to product shipping, receiving, to field handling. Electrostatic Discharge (ESD) causes millions of dollars worth of damage to electrical components, rendering circuit boards non-functional, and corrupting or erasing vital data. Often the damage is not detectable until a malfunction occurs. That could take weeks, months, or even years before an unpredictable and premature breakdown causes a field failure. If you use electronic components or boards in your products, adding devices that suppress ESD damage can result in preventing damage to your company reputation and bottom line. Other tangible benefits include: Higher manufacturing yields Less rework and inventory Reduced overall costs Fewer field failures and warranty calls Increased product reliability More repeat business Companies can also face legal liabilities if the product fails due to ESD/Transient damage. So it is important to include ESD/Transient Immunity in all phases of the project. It is wise to factor Electrostatic Discharge (ESD) Immunity strategies early in design processes. If a device in development fails ESD immunity tests-the scramble to avoid complete redesign often leads to higher parts cost and more manual assembly during manufacturing. There is little time to fully analyze which components do and do not provide ESD immunity. Worse, under pressure, finding comprehensive information tailored to ESD immunity design is very difficult, leaving your product vulnerable to ESD/Transient damage. Littelfuse associates can help you address these challenges, offering extensive application expertise and product testing capabilities. Please contact your local Littelfuse representative for assistance. ESD Suppression Strategies and Standards

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