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horizon Junior Member Offline Posts: 16	DAC 13 bits... piece of advice Sep 17^th, 2007, 4:47am Hi, I would like design a DAC 13bits, this one should be differential, no problem if it is slow, and it should not consumme a lot. I don't know how to begin. Does somebody can give me a piece of advice on the topology I should investigate ? resistor based, capacitor based, current source based ? thank you very much Horizon
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carlgrace

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Posts: 231
Berkeley, CA

Re: DAC 13 bits... piece of advice
Reply #1 - Sep 19^th, 2007, 7:37am

If it can be slow, you should look at an indirect approach, such as delta-sigma. It could significantly reduce the complexity. Resistor, capacitor and current source matching at 13 bits is difficult unless complex countermeasures are undertaken. Getting a delta-sigma DAC to be 13 bit accurate should be much easier.

Good luck,
Carl

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vivkr

Community Fellow

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Posts: 780

Re: DAC 13 bits... piece of advice
Reply #2 - Sep 19^th, 2007, 11:39pm

Hi,

One more method would be to use a cyclic DAC. Just like a cyclic ADC, this one generates the final output by generating
the individual step outputs serially. Some references may be found in the book by Jacob Baker, and in one paper by Marshall Bell
of National Semiconductor (JSSC - Dec '06 I think but it is not very old). The paper is on display drivers.
You can also try using dithering schemes to randomize the errors, and use 2 DACs in parallel if you always need a valid output (normally the case).

However, I agree with Carl that mismatch is a painful thing at 13bit levels. A delta-sigma approach helps a lot in such a case. You can
also consider using direct-charge-transfer buffers at the end to save on power.

Regards
Vivek

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loose-electron Senior Fellow Offline Best Design Tool = Capable Designers Posts: 1638 San Diego California	Re: DAC 13 bits... piece of advice Reply #3 - Sep 27^th, 2007, 1:03pm sigma delta or PWM oversampling architectures are most viable here. Put all the brains into the digital side of the system and minimize the analog. Add a sample/hold at the output, with refresh capabilty if needed.
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