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# how to calculate the physical size?

Last post Thu, Oct 1 2009 11:47 AM by TomBelpasso. 2 replies.
 Started by learnlearn1 17 Sep 2009 08:09 PM. Topic has 2 replies and 2678 views
• #### Thu, Sep 17 2009 8:09 PM

how to calculate the physical size?
 Hi all, I find the following info from osu018_stdcells.lef about Nand2x1gate. I need the phyiscal size of the gate, so I calcuate in this way:          2.4*10*lamda^2= 0.776 um^2 But this area seems too small. Any help? thanks! ----------------------------------------------------------- MACRO NAND2X1  CLASS  CORE ;  FOREIGN NAND2X1 0.000 0.000 ;  ORIGIN 0.000 0.000 ;  SIZE 2.400 BY 10.000 ;  SYMMETRY X Y  ;  SITE core ;  PIN A    DIRECTION INPUT ;    PORT      LAYER metal1 ;        RECT 0.200 2.900 0.600 3.700 ;    END  END A  PIN B    DIRECTION INPUT ;    PORT      LAYER metal1 ;        RECT 1.800 5.300 2.200 6.100 ;    END  END B
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• Post Points: 35
• #### Mon, Sep 28 2009 11:47 PM

• KVBABU
• Joined on Thu, Jul 23 2009
• Posts 30
• Points 610
Re: how to calculate the physical size?
 Hi The physical size of a standard cell is given in the lef. You need not multiply it with any factors like lamda. But you consider technology or length of gate of transistor , that must be equal to lamda divided by 2, to adapt lamda based design rules.Regards,VB  K.VISWANADH BABU
• Post Points: 5
• #### Thu, Oct 1 2009 11:47 AM

• TomBelpasso
• Joined on Sun, Aug 23 2009
• Saratoga, CA
• Posts 8
• Points 85
Re: how to calculate the physical size?
 I looks like you truncated the LEF, because the power pins were not included.One thing to be aware of is that most libraries have overlapping power rails, so the size in the LEF is actually smaller then the actual extent of the cell layout.  So the area in LEF will be smaller then what the layout tool will think the size of the cell is. The LEF size is usually represented as a boundary in the layout view.Since the cells are overlapped, you should use the LEF size when calculating the actually used area.  When calculating area using LEF, it will be slightly smaller by the width of one power rail in Y dimension, because the rails will stick out by 1/2 rail width at the top and the bottom of a cell cluster.Regards,- Tom BelpassoIntegrated Vision
• Post Points: 5