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Alan Walsh

Challenges & Requirements: Voltage Reference Design for Precision Successive-Approximation ADCs, Part 4

Alan Walsh
AlanWalsh
AlanWalsh
5/27/2014 10:02:07 AM
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Newbie
Re: Parasitics??
Hi Amrutah,

You are correct it is a bit of a delicate balance between insuring the driving circuit is stable but not too much series resistance or it will introduce reference droop which can be seen as a throughput dependent gainerror or worse (nonlinearity). The good news is that generally with such a large cap the driving buffer becomes seriously overdamped and almost can't oscillate but this has to be checked on a case by case basis.

Best Rgds,

Alan

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chirshadblog
chirshadblog
5/26/2014 5:19:04 AM
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Newbie
Re: Parasitics??
@amrulah: Well yes indeed but it's a common issue to all the items isn't it? Nothing wrong with the manufacturer itself I guess

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amrutah
amrutah
5/24/2014 10:38:10 AM
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Master
Parasitics??
Alan,

   I agree that the reservior capacitor should be place very close with low ESR. But other important routes are

1> from the capacitor to ADC

2> ADC-capacitor array to ADC ground reference.

   The ESR can be a factor for the stability of the reference system, but the series resistance can cause significant drop and leads to wrong reference value and hence the ADC conversion accuracy.

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amrutah
amrutah
5/24/2014 10:32:41 AM
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Master
Re: Best Articles
@sandrad:

What is this Behance Jeremy Renner link for.  

Is it your name or an adv.?

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sandrad.jerome
sandrad.jerome
5/22/2014 9:01:22 AM
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Newbie
Best Articles
I researched lot of articles and the best I came across is yours. Behance Jeremy Renner

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More Blogs from Alan Walsh
Once the drive capability has been determined, we must ensure that the noise from the reference circuit does not affect the ADC’s performance.
The voltage reference may integrate a buffer that has sufficient drive current. Otherwise, a suitable op amp can be used as a buffer.
The overall precision of a high-resolution, successive-approximation ADC depends on the accuracy, stability, and drive capability of its voltage reference.
How much power does your ADC draw? The spec sheet may provide the answers -- but read the fine print.
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