I am designing a small PCB (1"x1") and it will have some DC logic traces (5V and GND) and some high frequency AC power traces (100V 1000Hz 50mA). Are there any special considerations I need to take for isolating these from each other, more so than I do for a typical all-DC board?

  • \$\begingroup\$ That's not that high a frequency, all things considered. The voltage is worth looking after though. \$\endgroup\$ – Ignacio Vazquez-Abrams Aug 30 '12 at 18:39
  • \$\begingroup\$ I hope that AC is a sine; a 100 V, 1kHz square wave is a powerful radiator. \$\endgroup\$ – stevenvh Aug 30 '12 at 18:40
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    \$\begingroup\$ @IgnacioVazquez-Abrams well, I meant "higher than mains", not necessarily high-as-in-RF \$\endgroup\$ – Sparr Aug 30 '12 at 18:43
  • \$\begingroup\$ @stevenvh yes, it's a sine wave \$\endgroup\$ – Sparr Aug 30 '12 at 18:43
  • \$\begingroup\$ Is it a 2-layer board? What is the DC bit doing? \$\endgroup\$ – Oli Glaser Aug 30 '12 at 18:59

A good starting point would be to use UL creepage and clearance guidelines.

If the LVDC and AC don't require galvanic isolation, you can use UL's guideline for functional insulation, which is 40V/mil or 1.6kV/mm. This should eliminate any potential risk of flashover between the HV and LVDC.

  • \$\begingroup\$ Unforunately, the UL creepage guidelines are arcane to the point of being opaque, and things like the IEC standards are locked up behind pay-walls. I asked a similar question here. \$\endgroup\$ – Connor Wolf Sep 1 '12 at 11:02

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