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macro shot of a PCB with a squiggly trace on it

It's on pin 14, which is the master clock input (MCLK) of a WM8761: Low cost stereo DAC. I'm guessing it's meant to act as a small inductor? But why would you want that on a clock input?

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endolith
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1 Answers1

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It's a serpentine track. They are often used where equal track lengths are required with high-speed designs. In this case it is probably used to implement a very short delay.

Leon Heller
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    They're everywhere on computer motherboards, because they use lots of high speed busses. Take a look! – Connor Wolf Aug 26 '10 at 20:58
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    20 ms is 50 hz. I think you mean 20ns. – Connor Wolf Aug 27 '10 at 05:15
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    Apparently related terms: "skew minimization", "skew control", "serpentine delay", and you can do a trombone shape instead? – endolith Aug 27 '10 at 14:11
  • That trace doesn't look like it's part of a bus...so how would it be used for matching propagation delays? – ajs410 Aug 27 '10 at 19:43
  • @ajs410 - The other traces may be on the other side of the board, or on internal layers. Remember, in this context, "Bus" basically means any place with more than one high speed data signals. It can be as few as two traces (Data, clock). – Connor Wolf Aug 28 '10 at 05:41
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    @endolith, you can do other shapes, but you generally don't want the very beginning of the trace running too close to the very end, since they will couple together capacitively. – Connor Wolf Aug 28 '10 at 05:42
  • @ajs410: There are other DACs on the board, also with these, of different shapes. – endolith Aug 28 '10 at 16:00
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    @ajs410: My guess would be that the device producing the data and clock for the device switches both simultaneously, and the squiggle helps ensure that the proper signal is registered first. Though that would seem an awfully short squiggle to have much effect. – supercat May 14 '11 at 15:08