Author Topic: Trace length deltas and frequency  (Read 811 times)

0 Members and 1 Guest are viewing this topic.

Offline Pack34

  • Frequent Contributor
  • **
  • Posts: 667
Trace length deltas and frequency
« on: September 08, 2015, 02:37:13 pm »
In a project I'm working on, I have an odd setup. I'm sending low frequency analog waveforms to a device. Now this device has two sets of pins on opposite sides that need to be externally connected. By low frequency, I mean really slow (10-20Hz).

Is there some sort of rule-of-thumb for the allowable difference in trace lengths dependent on frequency? I can meander / trombone / snake the traces but at a higher voltage that I'm working with (150V), I'm thinking that it might cause more RF issues than it would solve... The delta I'm looking at would be on the order of 600mils. It's a lot, but given the wavelength of 20Hz, even at half the speed of light, is on the order of thousands of kilometers. It seems like the delta in my case would be a negligible percentage even in a desired low-noise setup like I'm working with.

If I were to meander / trombone / snake the traces to get everything to match, the general consensus for that would be to make sure that there is proper isolation per the voltage (16mils) between the traces and that there is no ground plane between the arcs?
« Last Edit: September 08, 2015, 02:44:38 pm by Pack34 »
 

Offline T3sl4co1l

  • Super Contributor
  • ***
  • Posts: 14089
  • Country: us
  • Expert, Analog Electronics, PCB Layout, EMC
    • Seven Transistor Labs
Re: Trace length deltas and frequency
« Reply #1 on: September 08, 2015, 03:12:02 pm »
Trace length is about 5 ps per mm.  How much difference does a few nanoseconds make?

Tim
Seven Transistor Labs, LLC
Electronic design, from concept to prototype.
Bringing a project to life?  Send me a message!
 

Offline MagicSmoker

  • Super Contributor
  • ***
  • Posts: 1288
  • Country: us
Re: Trace length deltas and frequency
« Reply #2 on: September 08, 2015, 03:19:37 pm »
You are about 6 orders of magnitude too low in frequency to even begin to worry about matching trace lengths...

More specifically, you only need to use meanders when you have critical timing requirements for clocks and usually the datasheet for any IC with such a requirement will specify the maximum amount of delay or skew.

 


Share me

Digg  Facebook  SlashDot  Delicious  Technorati  Twitter  Google  Yahoo
Smf