Binary weighted capacitor array in DAC

[pseudockb]

Hi, I am currently design a 12-bit SAR ADC. I am using the binary weighted capacitor array as the DAC. I'm wondering is there a way to split the capacitor array in a way such that only capacitors corresponding to the smallest 6 bit need to match to 12-bit resolution while the larger 6-bit can be matched to a lower resolution? Thanks

 

[sunking]

it is diffcult to get 12bit.
you can search some paper about "error average" or "digital calibration"