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 ?
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 ?
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
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
jcx said: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!
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.
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 ?
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 said: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.
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