Wire inductance on PCB,is this right ?

Discussion in 'General Electronics Chat' started by majd-ghadab, Jul 16, 2013.

  1. majd-ghadab

    Thread Starter New Member

    Dec 25, 2012
    12
    0
    Hello everyone
    i want to made impedance on specific frequency between tow pads on the PCB
    i am using altuim designer (length tuning) to have a specific wire length , so if i used this site :
    http://chemandy.com/calculators/flat-wire-inductor-calculator.htm
    to calculate 55 nH with 6 cm wire length, 0.2 cm width , and as in picture i have put this length between the pads do i get the inductance required inductance between them ??
     
  2. kubeek

    AAC Fanatic!

    Sep 20, 2005
    4,669
    804
    A snake like that will be mostly non-inductive, that´s why these shapes are used to match the length of traces like for example differential pairs to DRAM.
    You need a spiral shape or simply just a piece of arc to get inductance.
     
    bug13 likes this.
  3. majd-ghadab

    Thread Starter New Member

    Dec 25, 2012
    12
    0
    so you mean if i used this shape it will kill the inductance ?
    and why do they use tow equal wires lengths positive and negative >> to remove the inductive affect between each other ?
     
  4. kubeek

    AAC Fanatic!

    Sep 20, 2005
    4,669
    804
    You see that the current goes in such way that the magnetic field of each wire going left is cancelled by the wire going right, so the whole pattern should have almost no inductance. Noninductive resistors are done in a similar way.

    Designers use this to match the length of the data lines, so that the delay in them is the same on all the data pins. At high data rates this really starts to matter.
     
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