The question is; how to choose the unity capacitance for SAR ADC from the design kit. I am using 90nm from CMP, in their manual, they mentioned  cmin and ctype and cmax, what does that suppose to mean?

The solution is to use the standard deviation of the fractional matching error between two adjacent square capacitors which was modelled as,

δ=Ac/S
Where S is one side of the capacitor in µm. The value of AC is technology dependent and its unit is um as well, There is no such definition in their design kit just there is a section called matching Does that means that AC is equal to “matching” ?

I asked it from them but they just simply did not reply to me. I would appreciate if anybody could help in this regard.