Sidactor Protection Thyristor Products Page 20 SIDACtor Protection Thyristor Products

SIDACtor Protection Thyristors 2017 Littelfuse, Inc. Specifications are subject to change without notice. Revised: 02/23/17 Telecommunications Protection (continued) Because the interface portion of a Printed Circuit Board (PCB) is subjected to high voltages and surge currents, consideration should be given to the trace widths, trace separation, and grounding. Trace Widths Based on the Institute for Interconnecting and Packaging Electronic Currents, IPC D 275 specifies the trace widths required for various current-carrying capacities. This is very important for grounding conditions to ensure the integrity of the trace during a surge event. The required width is dependent on the amount of copper used for the trace and the acceptable temperature rise which can be tolerated. Littelfuse recommends a 0.025-inch trace width with one ounce copper. (For example, a 38-AWG wire is equal to approximately 8 mils to 10 mils. Therefore, the minimum trace width should be greater than 10 mils.) 0 .125 .25 .50 1 2 3 4 5 8 12 0 1 10 20 100 150 300 400 500 600 700 Conductor Cross-Section Area (sq mils) 5 30 50 70 200 250 6 10 15 20 25 30 Current in Amperes .75 1.5 7 10 C 20 C 30 C 35 45 C 60 C 75 C Allowable Temperature Rise Figure 1.5 Current versus Area The minimum width and thickness of conductors on a PCB is determined primarily by the current-carrying capacity required. This current-carrying capacity is limited by the allowable temperature rise of the etched copper conductor. An adjacent ground or power layer can significantly reduce this temperature rise. A single ground plane can generally raise the allowed current by 50 percent. An easy approximation can be generated by starting with the information in Figure 1.5 to calculate the conductor cross- sectional area required. Once this has been done, refer to Figure 1.6 for the conversion of the cross-sectional area to the required conductor width, dependent on the copper foil thickness of the trace. .350 .300 .250 .030 .010 .005 .001 0 1 10 20 100 150 300 400 500 600 700 Conductor Cross-Section Area (sq mils) 5 30 50 70 200 250 Conductor width in inches .050 .020 0 .070 .100 .150 .200 (1 oz/ft 2 ) 0.0014" (1/2 oz/ft 2 ) 0.0007" (2 oz/ft 2 ) 0.0028" (3 oz/ft 2 ) 0.0042" Figure 1.6 Conductor Width versus Area Trace Separation Tip and Ring traces are subjected to various transient and overvoltage conditions. To prevent arcing between traces, minimum trace separation should be maintained. UL 60950 provides additional information regarding creepage and clearance requirements, which are dependent on the Comparative Tracking Index (CTI) rating of the PCB, working voltage, and the expected operating environment. For additional information refer to the UL 60950-1 summary in the Regulatory section of this catalog. A good rule of thumb for outside layers is to maintain a minimum of 18 mils for 1 kV isolation. Route the Tip and Ring traces towards the edge of the PCB, away from areas containing static sensitive devices. Section continues on next page.

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