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venki_vlsi

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warangal

regarding DAC output impedance calculation
May 13^th, 2007, 9:32pm

hi,i am designing 10 bit DAC with sinlge ended output.
I want to know how much output impedance is required �for single current source to acheive sfdr of 60db and inl of 1 lsb.
I searched many papers ,they r giving for differenctial output impedance. Is there any relation to find outimpedance for single ended ouput i from differenal output �having same sfdr and inl. I am not sure if this valids ( 2*differentaloutput impedance=single ended outout imopedance).
Thanks in advance.

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s.venkat_nitw

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ywguo Community Fellow Offline Posts: 943 Shanghai, PRC	Re: regarding DAC output impedance calculation Reply #1 - May 15^th, 2007, 1:24am venki, Just calculate the output impedance regardless your DAC is differential output or single-ended output. If your DAC is single-ended output, the result is impedance for single-ended output. If your DAC is differential, the result is impedance for differential output. I think so. Yawei
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venki_vlsi Junior Member Offline Posts: 29 warangal	Re: regarding DAC output impedance calculation Reply #2 - May 16^th, 2007, 2:12am Thanks for ur reply.
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neoflash

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Mixed-Signal
Designer

Posts: 397

Re: regarding DAC output impedance calculation
Reply #3 - Mar 22^nd, 2011, 10:47pm

venki_vlsi wrote on May 13^th, 2007, 9:32pm:

hi,i am designing 10 bit DAC with sinlge ended output.
I want to know how much output impedance is required �for single current source to acheive sfdr of 60db and inl of 1 lsb.
I searched many papers ,they r giving for differenctial output impedance. Is there any relation to find outimpedance for single ended ouput i from differenal output �having same sfdr and inl. I am not sure if this valids ( 2*differentaloutput impedance=single ended outout imopedance).
Thanks in advance.

Single ended and differential current steering DAC suffer distortion from different mechanism.

Differential DAC can cancel HD2 and suffer only HD3 which is a lot lower.

Single ended DAC suffer HD2 which is approximated by

(RL/Ru)*2^N/4

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