wilner@motcid.UUCP (Corey S. Wilner) (02/22/91)
I have an interesting design problem. I need to protect a Cheapernet LAN tap from voltage surges. I have to pass a specification that states either 800 or -800 volts can be applied to my BNC center conductor with respect to the outer ground conductor. Some of you may just jump up and say "use a transorb" or "use a zener". However, here is where the problem lies. The capacitance seen at the coax tap must be less than 8pf. Yes, thats 8pf. How can I protect against surges while still meeting my capacitive load limitations. Please post circuit ideas with any comments you may have. ******************************************************** Corey S. Wilner | | __o Motorola Cellular | ..!uunet!motcid!wilner | -\<, 708-632-7206 | motcid!wilner@uunet.UU.NET | O/ O ********************************************************
cjp@megatek.UUCP (Christopher J. Pikus) (02/25/91)
From article <4480@mint17.UUCP>, by wilner@motcid.UUCP (Corey S. Wilner): > I have an interesting design problem. I need to protect a Cheapernet > LAN tap from voltage surges. I have to pass a specification that > states either 800 or -800 volts can be applied to my BNC center conductor > with respect to the outer ground conductor. > > ******************************************************** > Corey S. Wilner | | __o > Motorola Cellular | ..!uunet!motcid!wilner | -\<, > 708-632-7206 | motcid!wilner@uunet.UU.NET | O/ O > ******************************************************** Corey, From several of the ethernet cards that I have seen, many designers solve this with a NEON BULB connected accross the BNC. It should present almost no capacitance and have high breakdown voltage. A dropping resistor is optional (although I never saw one used). -- Wax your board, waste your brain, and pray for waves... Christopher J. Pikus, Megatek Corp. INTERNET: cjp@megatek.uucp San Diego, CA UUCP: uunet!megatek!cjp or ucsd!megatek!cjp