SV: Re: [sdiy] 16bit DC, DAC, SPI!

[Eric Brombaugh]

Bruce Duncan wrote:
>> The LTC1655 looks pretty nice. I've also got an application that uses 
>> the LTC26x4 quad SPI DAC. They're around $5-$10 (non-stock @ Digi-Key 
>> however) depending on resolution (12, 14, or 16). Small package, but the 
>> SPI clock rate is 50MHz so you can use them for fast sample rates. Plus 
>> the DNL is better than 0.2LSB on the 16-bit part!
> 
> Isn't it the accuracy or Integral Nonlinearity in LTC speak that is the 
> more important spec for DC.
> In the LTC1655 case it is +/-8 LSB same as the AD5663

Yes, INL is a critical parameter. The worst-case for the LTC1655 gives 
it only 11.5 bits accuracy (13-bits typical). The AD5663 seems to call 
this 'relative accuracy' and worst-case boils down to 12 bits (13 bits 
typical). For the LTC26x4 its max range limits the part to more like 
10-bit accuracy worst case (14-bit accuracy typical).

So it looks like the AD5663 comes out ahead worst-case. Available in 
single quantities from Digi-Key for $8.83. Main downside is ~200kHz 
sample rate (no biggie for CVs) and 10-pin MSOP package.

For small SMDs in SDIY applications I've had good luck with DIP - 
MSOP/SSOP adapters - once you've done one or two of those you'll get the 
hang of it and they come out nice and clean. You can get the adapters 
from Mouser in panels and just snap them off as you need them. Google 
Bellin Dynamic Systems for part numbers.

Eric