How to select the Cl when design a current-steering DAC?

[stpluto]

In some papers and datasheets, there are a big capacitor at the output which in parallel with the load resistor.
For example: in the ADV7125, Cl=10pF **broken link removed**
In " A 12-Bit Intrinsic Accuracy High-Speed CMOS DAC," IEEE JSSC Dec 1998, Cl=10pF
Why they use so big capacitor and how to choose the value of the capacitor?

 

[jerryzhao]

It's not the external capacitor. It is PAD and Loading's parasitic capacitor, that is about 10Pf

 

[stpluto]

u mean the pad and the external loading's parasitical capacitors is about 10pF?
can u give me more info about this?