Sky130 Pdk

Sky130A PDK Skill

Use this skill for Sky130A ngspice work with the open-source SkyWater/open_pdks PDK. It covers PDK installation, model-path discovery, process corners, process Monte Carlo, and small smoke examples.

Do not commit the PDK data itself. The sky130A/ runtime tree is installed outside the project, usually through Volare.

Quick Start

Install the PDK with Volare:

python3 -m pip install --user volare
export PATH="$HOME/.local/bin:$PATH"
volare enable --pdk sky130 c6d73a35f524070e85faff4a6a9eef49553ebc2b

Run smoke examples from the skill directory:

cd sky130-pdk
python3 assets/run_sky130_mos_iv_pvt_mc.py
python3 assets/run_sky130_ringosc_pvt_mc.py
python3 assets/run_sky130_five_transistor_ota_pvt_mc.py

Each script also accepts:

--pdk-root <path-containing-sky130A-or-sky130A-itself>
--workdir <output-directory>
--mc-runs <N>
--jobs <parallel-ngspice-jobs>

Run direct ngspice examples:

export PDK_ROOT="$(volare path)/volare/sky130/versions/$(volare output --pdk sky130)"
cd examples/ota-5t
ngspice -b tb.spi

Model Entry

Prefer the continuous model library for PVT/Monte Carlo smoke:

sky130A/libs.tech/combined/continuous/sky130.lib.spice

Use .lib sections:

.lib ".../sky130.lib.spice" tt
.lib ".../sky130.lib.spice" ff
.lib ".../sky130.lib.spice" ss
.lib ".../sky130.lib.spice" fs
.lib ".../sky130.lib.spice" sf
.lib ".../sky130.lib.spice" mc

Common primitive devices:

Xn d g s b sky130_fd_pr__nfet_01v8 l=0.15 w=1.0 nf=1
Xp d g s b sky130_fd_pr__pfet_01v8 l=0.15 w=2.0 nf=1

The continuous Sky130 models use micron-valued l and w parameters in these examples.

Included Smoke Examples

• run_sky130_mos_iv_pvt_mc.py: NMOS Id-Vgs smoke across tt/ff/ss/fs/sf plus MC current spread.
• run_sky130_ringosc_pvt_mc.py: three-stage CMOS ring oscillator PVT/MC frequency smoke.
• run_sky130_five_transistor_ota_pvt_mc.py: five-transistor OTA low-frequency AC gain PVT/MC smoke.
• examples/: three circuit folders, each with circuit.scs/.spi and a standalone tb.scs/.spi.

The ring oscillator and OTA examples belong in this skill because they are Sky130A PDK smoke/application examples. They are not generic ngspice tutorials and should not be placed in the PTM transistor-model library.

Sky130 SCS To ngspice Sky130

ngspice does not parse full Spectre .scs syntax. This skill includes a small Sky130-oriented converter for user circuit netlists:

Use --fragment when converting a user circuit/subcircuit file that will be included by another testbench. Fragment mode suppresses the auto-inserted model library, control block, and final .end:

python3 assets/scs_sky130_to_ngspice_sky130.py examples/ring_oscillator/circuit.scs \
  --fragment -o /tmp/ring_oscillator.spi

The converter intentionally supports only a practical subset: parameters, include ... section=, local .scs includes, options, subckt/ends, Sky130 subcircuit instances, vsource/isource, vcvs, R/C/L passives, save, ic, measure/meas, simple tran/dc/ac/noise analyses, and basic ngspice .control pass-through. It does not translate the Sky130 PDK model files themselves; output netlists reference the installed ngspice model library.

Standalone examples are in examples/:

• ring_oscillator/circuit.scs plus ring_oscillator/tb.scs.
• ota-5t/circuit.scs plus ota-5t/tb.scs.
• amp-2s-miller/circuit.scs plus amp-2s-miller/tb.scs.

Convert a standalone Spectre-style testbench directly:

python3 assets/scs_sky130_to_ngspice_sky130.py examples/ota-5t/tb.scs -o /tmp/ota-5t_tb.spi
ngspice -b /tmp/ota-5t_tb.spi

References

Read these only when needed:

• references/installation.md: installing Volare/Sky130A and locating PDK_ROOT.
• references/ngspice-corners.md: ngspice .lib sections, PVT/MC usage, and troubleshooting.
• references/five-transistor-ota-testbenches.md: guidance for extending the included OTA smoke bench.