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Recommended trace widths

Ted H
Intellectual 275 points


I'm developing a DLP/DMD system based on the LC4500 reference design.  Layout recommendations specify 50 ohm traces on one hand, but also recommend different minimum trace widths for data/control lines (5 mil) and clocks (7 mil).  How can these seemingly contradictory recommendations be reconciled?  Can traces of different widths have the same impedance? 

Also, I noticed that TI is recommending trace widths for VREF, VBIAS, VRESET and VOFFSET to be 15 mils.  That seems excessive considering the maximum current (on VBIAS) is 3.55 mA.  It is difficult enough laying this out near the interposers with 5 mil traces.  Am I missing something here?

  • 0
    TI__Expert 4720 points

    Hello Ted,

    I apologize for the delayed response. With regards to the trace widths, the most important aspects for your hardware layout and that the traces have matched lengths and 50 ohm impedence. Adjust the trace widths accordingly. Could you point me to were you saw that recommendation very specifically (document number, page, etc.)?

    We recommend the wide trace widths for the power lines because of the transient loads that occur during DMD operation. The average current is 3.55mA for VBIAS, but some power lines can have loading transients around 200mA during operation. The transient loading is also why we recommend proper capacitance near the power pins on the DMD.

    Hope this helps!

    Best regards,

    Blair