voltage reference for 16bit dac (LM329 ?)

[ash_dac]

Hi,

I need a 2.5V, and a 3.3V reference voltage for a dac.

I've built some voltage references with band-gap but after doing some reading I think I need to move to buried zener.See :- http://focus.ti.com/lit/an/slyt183/slyt183.pdf

I was thinking of using a LM329 with a voltage divider into a voltage follower:- http://www.diyaudio.com/forums/showthread.php?postid=300396#post300396

Any thoughts ?

 

[jcx]

http://www.cirrus.com/en/pubs/appNote/an04.pdf

applies to dacs as well

for audio dynamic specs are most important, absolute accuracy, drift, tempco are all secondary -- filtered bandgaps are fine

analog.com also has the newer Vref "xfet" technology -- but really lousy data sheet info, only audio noise spec is "60 nV/rtHz", no noise density vs freq, output Z has linear impedance axis and stops short in frequency of the likely Cload peaking

 

[ash_dac]

http://www.cirrus.com/en/pubs/appNote/an04.pdf

applies to dacs as well

for audio dynamic specs are most important, absolute accuracy, drift, tempco are all secondary -- filtered bandgaps are fine

analog.com also has the newer Vref "xfet" technology -- but really lousy data sheet info, only audio noise spec is "60 nV/rtHz", no noise density vs freq, output Z has linear impedance axis and stops short in frequency of the likely Cload peaking

Thanks.

I've been using bandgaps into oscon SA capacitors. I think I need to plot the graphs!

 

[jackinnj]

the Crystal application note is really useful -- if you use one of the buffered circuits be mindful that errors can be caused by the bias current flowing from the input pins of the buffer. (Not my original thought -- pointed out by Ron Mancini from TI a couple years ago in an apnote). So you can't just slap any old opamp into the filter circuit -- use an ultra low bias current opamp.

 

[ash_dac]

zmr25h ?

Hi,

I've been looking at this part zmr25h (used here:- http://www.diyaudio.com/forums/showthread.php?postid=300396#post300396)

http://www.zetex.com/3.0/pdf/zmr25h.pdf

Any thoughts on this part ?

 

[jcx]

you need to look at the DAC data sheet and see what sort of load it presents to the Vref to start the engineering of a Vref circuit

 

[ash_dac]

you need to look at the DAC data sheet and see what sort of load it presents to the Vref to start the engineering of a Vref circuit

Reference voltage output is listed as 2 ohms at 2.5V. I believe that's the output from the internal reference circuit at pin 16.