The simulation is carried out using ngspice using the mixed-mode xspice capabilities. The digital section is synthesized using yosys that can then be bridged to/from the analog section.
The Schematics are created using xschem, which also serves as the simulation framework.
The SAR schematic:
The simulation output can then be viewed in both analog and digital domain.
Digital waveforms displayed using GTKWave
Analog waveforms displayed using Gnuplot in interactive mode.