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  1. #1
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    Rplpoly layout matching problem

    Hi,

    I am making 6bit R DAC (i.e. 64 resistor) with resistor value 300 ohm. After makin layout of my r string the layout resistor values are slightly different. The top and the bottom resistor values are more different than the pre simulation value. I am using maximum identical contacts and placing to make them matched. I am taking rplpoly for my resistor layout.

    Please suggest..How I can make these resistor value identical in the layout.


    Thanks

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  2. #2
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    Dominik Przyborowski's Avatar
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    Re: Rplpoly layout matching problem

    Compare netlist. How resistors are instantiated in schematic netlist and what is added into extracted netlist.



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  3. #3
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    Re: Rplpoly layout matching problem

    If it's applicable - You can adjust the physical W/L dimensions in order to match the resistor for different values.



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  4. #4
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    Re: Rplpoly layout matching problem

    Case 1: You put in identical schematic values and you
    got (SDL synthesis) non-identical layout dimensions.
    This would seem improbable.

    Case 2: You got identical resistor segment geometries
    but the extracted values are off by an integer multiple /
    divisor. This might be a hookup error putting two links
    in series or parallel.


    Case 3: You got identical resistor segment geometries
    but the extracted values are off by an arbitrary small
    amount. This might be from "too much smarts" in the
    layout extraction "doing things" to the extracted value
    for stuff like proximity effects. Try putting 66 elements
    and tying off the end ones to themselves, as "dummies".



  5. #5
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    Re: Rplpoly layout matching problem

    How did you figure out the top and bottom resistance difference, and are those bigger or smaller values? How many contacts you have now, which layer are you using for wiring at the top/middle/bottom?
    "Try SCE to AUX." /John Aaron/



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  6. #6
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    Re: Rplpoly layout matching problem

    Can you show the layout and the (post-layout) netlist?



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