In a message dated 8/11/2003, do...@aiinet.com writes:
How can I determine the best line spacing for high voltage pulses on differential pairs? Should the voltage be calculated at protection device's clamping voltage? How does the formula change for interlayer vs. top/bottom layer? Is there any good reference material? Hi Doug: If your question is what level of voltage-withstand you need to maintain between the conductors of a differential pair, you are pretty much on the right track by tying it to the maximum trigger voltage of the differential protection device. With a protection device that triggers in the range of 350 volts worst case, the spacing can be quite small, on the order of 0.3 mm. For this condition, any layer-to-layer separation will be more than adequate. For differential pairs that have such a protection device, a key issue that I have seen some people overlook is that after the fuse blows during the Level 2 power cross tests, the voltage tip-to-ring will reach 600 VRMS in the section between the network connector and the fuse. Any arcing under this condition will cause the wiring simulator to open, resulting in a failure of the test. I would suggest tip-to-ring spacing of at least 1.5 mm for this area. The issues regarding spacing get more complex when you are looking at pair-to-pair or pair-to-ground separation. In that case you will be dealing with voltages up to 2500 volts peak under the Level 1 surges in GR-1089. However, your question seems to be targeted at the separation between two conductors of a differential pair, which I have tried to address above. Joe Randolph Telecom Design Consultant Randolph Telecom, Inc. 781-721-2848 j...@randolph-telecom.com http://www.randolph-telecom.com
