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Design >> Analog Design >> Capacitor matching in 90nm CMP
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Message started by Leila on May 13^th, 2008, 3:07pm

Title: Capacitor matching in 90nm CMP
Post by Leila on May 13^th, 2008, 3:07pm

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.

Title: Re: Capacitor matching in 90nm CMP
Post by Berti on May 14^th, 2008, 12:11am

Capacitor matching depends on the area. Therefore one standard derivation is σΔC/C = AC/sqrt(W*L).
Since a gaussian distribution is assumed ctyp, cmin, and cmax refer to the mean value and ±x⋅sigma
derivation, respectively (x is usually 3 or 6).

Cheers