Spice Simulation

Add a small ngspice-backed testbench to a .zen design.

Workflow

-

Confirm the target is simulation-capable by running a dummy sim. pcb sim <path/to/file.zen> --setup "* empty setup check"

-

If the SPICE model is missing, add it.

Find a vendor model, download it, or create a simple behavioral model if needed. Wire it through the leaf component with spice_model=SpiceModel(...) before writing the testbench.

-

Create a focused testbench file.

Use a generic package-local path such as <package>/testbench/test_<scenario>.zen.

• Keep the structure simple:

• top docstring

• imports

• nets/interfaces

• module-under-test instantiation

• minimal external load or pull-ups

• one Simulation(...) block

• Put sources and analysis inside Simulation.setup.

Use raw ngspice for:

• DC

• PULSE(...)

• PWL(...)

• .control

• tran

• hardcopy

• Write the plot to testbench/output/<scenario>.svg.

Simulation In Zener

Simulation is a Zener property loaded from @stdlib/properties.zen and attached as a normal top-level object:

load("@stdlib/properties.zen", "Simulation")

Simulation(

    name="SIM",

    setup="""

* raw ngspice goes here

.control

  tran 10u 10m

.endc

""",

)

The setup string is passed through as ngspice input. Put voltage sources, waveform definitions, analysis commands, and plot/export commands there.

Pattern

"""<Part> <scenario> simulation test."""

load("@stdlib/properties.zen", "Simulation")

Target = Module("../Target.zen")

Resistor = Module("@stdlib/generics/Resistor.zen")

VIN = Power(voltage="12V")

VOUT = Power()

GND = Ground()

Target(

    name="UUT",

    VIN=VIN,

    VOUT=VOUT,

    GND=GND,

)

Resistor(

    name="R_LOAD",

    value="10ohm",

    package="0603",

    P1=VOUT,

    P2=GND,

)

Simulation(

    name="SIM",

    setup="""

* <Part> <scenario>

V_IN VIN GND DC 12

.control

  tran 10u 10m

  set hcopydevtype = svg

  hardcopy output/<scenario>.svg v(VIN) v(VOUT) title "<Part> <scenario>" xlabel "Time" ylabel "Voltage"

.endc

""",

)

Component Pattern

If the leaf component does not already expose a SPICE model, add one like this:

VIN = io(Power())

VOUT = io(Power())

GND = io(Ground())

Component(

    name="MyPart",

    symbol=Symbol(library="MyPart.kicad_sym"),

    pins={"VIN": VIN, "VOUT": VOUT, "GND": GND},

    spice_model=SpiceModel(

        "MyPart.lib",

        "MyPart_SUBCKT",

        nets=[VIN, VOUT, GND],

        args={},

    ),

)

Example Shapes

Load switch enable test:

V_IN VIN GND DC 5.3

V_ON ON GND PULSE(0 0.9V 1ms 10us 10us 3ms 5ms)

Protection threshold sweep:

V_IN VIN GND PWL(0 12 5m 12 5.1m 22 10m 22 10.1m 12 15m 12 15.1m 2 20m 2)

Notes

• Prefer one behavior per file: startup, enable/disable, OVLO/UVLO, current limit.

• Keep passives in Zener and keep sources in setup.

• Plot only the signals that prove the behavior.

• If a SPICE model is missing, obtain or create it first, then add the testbench.