@User xschem source distribution includes an example in

ngspice/delta_sigma.sch

. It is not a sky130 design, it uses generic 65nm models, however converting this design to sky130 could be easy. This is a very simple 1st order 6 bit adc Sigma-Delta converter. If you have xschem installed start xschem in your home directory (so it should not read the sky130 xschemrc setup). This is however a very stupid-simple design, as i am not a noise shaping-discrete time expert. May be you have very high frequency requirements and this design is not any help. But it is definitely possible to use xschem.

Thanks @User Now I think I should have started with exploring things closer to home first 😅 A follow up, is there a way to maybe include all of the sky130 models present in the open_pdk, not just the primitive ones with xschem?

@User currently sky130 integration of xschem includes process primitives (transistors, capacitors, resistors, diodes, reram) and standard cells. In particular all the sky130_fd_sc_hd__* symbols are available in the

sky130_stdcells/

library (this is the most used standard cell library, the high density variant). Standard cells in schematics are useful in mixed signal situations, where you have both analog and digital functions. 100% digital designs don't use a schematic at all as the design flow goes from HDL coding to GDS layout. If you are thinking to other sky130 primitives to include in xschem please let me know.

Okay, that explains my doubt. Thanks. If I ever need your help, I will be sure to post it here