TSMC28HPC+ Native Adapter

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Status: maintained adapter guide. Scope is the documented 0.9 V core MOS wrappers and the analysis paths listed below, not the complete iPDK.

The tsmc28hpcp binding evaluates a locally installed, licensed TSMC 28HPC+ model deck inside circuitopt. The default tsmc28hpcp.nmos and tsmc28hpcp.pmos model types do not launch ngspice: circuitopt parses the HSPICE library closure, resolves the foundry MOS macros and bins, and evaluates the resulting BSIM4.5 models through its bundled native compact-model backend.

The adapter targets the 0.9 V core nch_mac and pch_mac wrappers in the 1d8 HSPICE model deck. Foundry files remain local and must not be committed.

Model Entry

The portable project-local entry point is:

PDK/tsmc28hpcp/models/hspice/cln28hpcp_1d8_elk_v1d0_2p2.l

Only this main model file is required for the current core-device adapter; the complete iPDK delivery does not need to be copied into the repository. The licensed models/ payload is ignored by Git.

External installations can use:

export TSMC28_MODEL_DIR=/path/to/models/hspice
# or
export TSMC28_PDK_ROOT=/path/to/iPDK_delivery

Resolution order is TSMC28_MODEL_DIR, TSMC28_PDK_ROOT, the project-local entry, then PDK_ROOT/tsmc28hpcp. No machine-specific absolute path is stored in circuit JSON or Python source.

The vendored Berkeley BSIM4.5 device source is compiled into the circuitopt_core extension at build time (the co-bsim4 Rust crate drives the build), not on first use at runtime. Installing a released circuitopt-core wheel needs no compiler at all; building it from a source checkout needs a Rust toolchain (rustup) and a C compiler once, via maturin develop --release -m rust/crates/co-py/Cargo.toml. ngspice is not required for normal simulation.

Device Binding

{
  "devices": [
    {"name": "MN", "drain": "OUT", "gate": "IN", "source": "GND", "W": 1.0, "L": 0.03},
    {"name": "MP", "drain": "OUT", "gate": "IN", "source": "VDD", "W": 2.0, "L": 0.03}
  ],
  "models": {
    "MN": {"pdk": "tsmc28hpcp", "model": "nmos",
           "section": "inherit", "bin": "auto"},
    "MP": {"pdk": "tsmc28hpcp", "model": "pmos",
           "section": "inherit", "bin": "auto", "vb": 0.9}
  },
  "bias": {"VDD": 0.9}
}

Geometry is in micrometres. NF is passed through the foundry macro rather than approximated by scaling a one-finger result. PMOS bulk should normally be set explicitly to the 0.9 V core rail.

Supported corners are tt, ss, ff, sf, and fs; nom aliases tt. temperature is expressed in kelvin. Per-instance threshold mismatch is forwarded through the macro _delvto parameter.

Analysis Coverage

The native path supports:

• nonlinear DC and four-terminal operating-point currents;
• full four-terminal conductance and charge linearization for AC and PAC;
• correlated four-terminal white and flicker noise for noise and PNoise;
• charge-conserving backward-Euler and Gear2 transient integration;
• PSS shooting with an analytic full-terminal monodromy;
• PAC harmonic conversion and PNoise cyclostationary folding.

PNoise retains the terminal covariance matrix and extracts the foundry deck's flicker exponent instead of assuming every device follows exactly 1/f.

ngspice remains available only as an independent oracle. Bind every MOS to tsmc28hpcp_ngspice.nmos / tsmc28hpcp_ngspice.pmos, or use the helpers in circuitopt.ngspice_ac, when an explicit comparison against ngspice is wanted. Set NGSPICE_BIN only for that oracle path.

This adapter covers circuit simulation and optimization. Cadence library setup, layout, DRC/LVS, extraction, reliability checks, and tapeout sign-off remain responsibilities of the official installed iPDK and approved foundry tools.

Five-Transistor OTA Verification

The compact benchmark contains exactly five MOS devices and no ADC/CDAC logic:

python experiments/tsmc28_5t_ota_compare.py \
  --output /tmp/tsmc28_5t_compare.json
pytest -q tests/test_tsmc28_5t_ota.py

The comparison runs the same TSMC28 5T OTA through the native backend and the explicit ngspice oracle. It checks device Id/gm/gds, differential AC, output noise integrated from 1 kHz to 10 GHz, and a 2 mV differential input-step transient. The report contains fixed pass thresholds and a top-level passed flag.

The model remains subject to the user's foundry agreement/NDA. Keeping it in an ignored local directory prevents accidental Git publication; it does not alter the licensing terms.