supply.spi

ngspice/supply.spi

The supply corners, as parameters rather than sources. A testbench writes

.param AVDD = {vdda}
VDD  VDD_1V8  VSS  pwl 0 0 10n {AVDD}

and the corner decides the value.

Corner vdda vdde vddh
Vt typical 1.8 3.0 12
Vl low 1.7 2.4 10.8
Vh high 1.9 3.6 13.2

vdda is the 1.8 V core supply at ±5%. vdde is the 3.0 V IO supply, spread much wider (−20% / +20%) because that is what the IO devices have to survive. vddh is the 12 V high voltage domain at ±10%.