MOM capacitor problems for ADC

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heshufeng

Joined: 12 Jun 2009
Posts: 3

04 Nov 2009 12:29 MOM capacitor problems

hi all,
now i will use mom capacitor in my 65nm ADC, but i know nothing about it,
does the matching properity better than mim capacitor ?
will i split one larger capacitor (800fF) into some smaller capactiors in parallel?
and how to fix the metal length ? for long metal have large parasitical resistance, will it affact frequency response , or increase noise ?
please help me with these problems ,thanks in advance.

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timof

Joined: 21 Feb 2008
Posts: 86
Helped: 6

04 Nov 2009 19:43 Re: MOM capacitor problems

Metal finger length affects the resistance and thus quality factor (and frequency response). One more factor is parasitic series inductance (also affecting frequency response and resonant frequency). If you are using SAR ADC, capacitors are usually built from "unit capacitors" to achieve 1:2:4:... weighting.

On matching properties - you will have to refer to foundry's documentation.

You may also want to review the following related discussions:

http://www.edaboard.com/ftopic277873.html

http://www.edaboard.com/ftopic366048.html