[volt-nuts] Homebrew LTZ1000 reference?

[Ulrich Bangert]

Randy,

microcontrollers that feature pwm make excellent DACs if you put some clever
electronics around them. Have a look at

http://www.electronicsweekly.com/Articles/2008/10/30/44817/dc-accurate-32-bi
t-dac-achieves-32-bit-resolution.htm

for an example. I have build this circuit (with some resistor variations
because I needed to combine two 12 bit DACs into one 24 bit DAC) and have
found it to work like charme. I made stability measurements on the output
signal with my HP3457 (in high resolution mode over GPIB) which showed that
the voltage references low frequency noise (a LT1021 in my case) was to be
measured on the output down-divided by the pwm's on/off factor, i.e. the
output's signal noise stays the same RELATIVE to the output amplitude and is
basically the same as that of the reference itself.

Best regards
Ulrich  

> -----Ursprungliche Nachricht-----
> Von: volt-nuts-bounces at febo.com 
> [mailto:volt-nuts-bounces at febo.com] Im Auftrag von Randy Scott
> Gesendet: Donnerstag, 19. November 2009 17:00
> An: Discussion of precise voltage measurement
> Betreff: Re: [volt-nuts] Homebrew LTZ1000 reference?
> 
> 
> > Linear Technology has an application note
> > on this very subject:
> > 
> > cds.linear.com/docs/Application%20Note/an86f.pdf
> 
> Has anyone here actually built the 20-bit DAC described in 
> the app note?  I've been thinking about it and actually 
> started laying out a PCB.  I am hesitant to pull the trigger, 
> given that the DAC ICs that I was planning on using (LTC1595 
> in SO package) are $48 each and the design requires two of them.
> 
> Randy.
> 
> 
>       
> 
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