[sdiy] Re: Inexpensive 16 bit DAC?

[Bob Weigel]

Hmmm...now we're talking...about taking a 16 bit paralell line....here.  
And hooking the 8msb's to one 8 bit dac and the lsb's to the other.   
The lsb's obviously will produce a voltage that is accurate since that's 
what an 8 bit dac is designed to do...  THE PROBLEM is going to happen 
when we try to evaluate the upper 8 bits.  What do we do?  Multiply the 
analog voltage by 256 and then sum it with the output of the LSB dac's 
output right?  Indeed the slightest inaccuracy of the MSB DAC's output 
will be also multiplied by 256.  So if it's off by half a bit or 
something...throw away all your LSB data basically and be happy with 8 
bit.  I suggested the latch, resistor ladder and filter approach for 
econo...not that it's a few minute job to build.  You'd think there 
would be a nice off the shelf solution for not too much out there by 
now. I haven't followed it of late. -Bob

harrybissell wrote:

>This is like saying that if a woman can have a baby in nine months, two
>women can do the job in 4 1/2 months...   :^P
>
>In most cases, two 8 bit dacs would not give the perfromance of a 16 bit dac.
>You would be lucky to get maybe 12 bits out of it.  The accuracy you need just
>isn't there.
>
>I'm going to skip the math here... but Professor Magnus will prabably keep
>you all after class and make you clap the erasers...   :^P
>
>H^) harry
>
>Tim Parkhurst wrote:
>
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>>>-----Original Message-----
>>>From: Kevin Lightner [mailto:synthfool at synthfool.com]
>>>Sent: Friday, April 22, 2005 3:23 PM
>>>To: synthdiy
>>>Subject: [sdiy] Re: Inexpensive 16 bit DAC?
>>>
>>>      
>>>
>>>>Hi,
>>>>
>>>>I need to find an inexpensive and easy to get 16 bit parallel DAC for
>>>>        
>>>>
>>audio.
>>    
>>
>>>>Either DIP or SOIC is fine.
>>>>
>>>>Any suggestions?
>>>>
>>>>Thank you for any help.
>>>>        
>>>>
>>>Laugh as you might: use two 8 bit dacs.
>>>They're cheap and there's many parallel styles.
>>>
>>>--
>>>Regards,
>>>Kevin Lightner
>>>
>>>      
>>>
>>Hi Grant,
>>
>>If that approach (two 8-bit DACs) gives you the required accuracy, then you
>>might want to check out the TI TLC7528CN (PDIP 20) or TLC7528CDW (SOIC 20).
>>This is a dual 8-bit MDAC with data latches (and good matching between the
>>two converters). The A and B DACs have separate ref voltage inputs, so you
>>could set up a different voltage range for the 'high order' and 'low order'
>>bytes. Input is 8-bit parallel.
>>
>>Tim (1-bit processor) Servo
>>
>>"Imagination is more important than knowledge." - Albert Einstein
>>
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