[sdiy] Consider this DAC

[ASSI]

On Saturday 13 March 2010, Antti Huovilainen wrote:
> Yes, but the question was whether 12 bit dac would already be at
> the limit of the rest of the circuitry.

I didn't read the question this way, sorry for that misunderstanding.

A 12bit performance level implies 72dB SNDR over the bandwidth of 
interest (you don't want to use your CV just at DC).  Getting that 
sort of accuracy without calibration is already nontrivial and keeping 
it up through temperature requires extra care.  The noisefloor is also 
awfully close in most systems and not easily lowered by much.

> Delta-sigma is rather the other extreme of the accuracy scale.

Not necessarily.  Audio codecs have lousy DC specs because they don't 
need any accuracy in that department, but if you need something like 
14bit DC accuracy and an extra ten bit resolution, there's nothing to 
stop you from using a fast DAC plus modulator to get there.  You will 
need a DAC with a higher update rate, a better opamp and a filter at 
the output and it will become more difficult to multiplex a DAC, but 
otherwise it is "just" some extra code/hardware for the DAC control.  
It appears that AD is set to use this method to bump their 12Bit DAC 
up to 16bit resolution on the upcoming ADuC series that Eric has 
posted about a few days ago.



Achim.
-- 
+<[Q+ Matrix-12 WAVE#46+305 Neuron microQkb Andromeda XTk Blofeld]>+

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