How to decide Std. cell height and width??

[santhosh.mandugula]

why height fixed in stanadard cell

Hi, could you explain, how the height of a standard cell is fixed while developing a std. cell library. Is it height of a tallest cell, then which cell they will consider as tallest cell in a library??

How much should be the width of std. cell? Generally it is (6 X height) of std cell. Is it correct, is it a hard rule to follow??

regards,
santhosh

 

[Pat_Mustard]

Generally it is hard to have hard and fast rules for std cells, however your height should be sufficent for all std cells in a library no matter their power (ie you may be able to make x1 x2 x4 cells small in height, but if the x16 cell needs to be taller then all must be taller). Width is then miminimised for the power of the cell (x1 should have least width, x16 most and all shades of grey inbetween).
Height = Fixed
Width= Dependant on cell

 

[ravichandra]

Hi,

First thing is that the width of the standard cell is not fixed, but you need to make it as compact as possible.

And in fixing the height of the standard cell requires lot of study on performance of CMOS behavior for particular technology.

you need to evaluate on the requirements such as performance, density, power etc

 

[hdmi]

Hi,

The height is fixed as others mentioned, however when determining the height, it has a lot to do with the routability, for example, should it be 9 tracks or 11 tracks, the cell lib developers usually have to run a lot of P&R (Place & Route) experiments to determin the optimal height, which is multiple of tracks (or metal 1 pitch), and not always the smallest the better.