Device:
Sxxxxxxx (n+ n- nc+ nc-) modelname ic
Model (required):
.model modelname SW args
Device:
Wxxxxxxx (n+ n- ce) modelname ic
Model (required):
.model modelname CSW args
Voltage or current controlled switch.
N+ and n- are the positive and negative element nodes, respectively.
For voltage controlled switch, Nc+ and nc- are the controlling nodes.
For current controlled switch, ce is the name of a controlling element.
Modelname is the model name.
A switch is a resistor between n+ and n-. The value of the resistor is determined by the state of the switch.
| control | resistance |
|---|---|
| vc > von ic > ion | Ron |
| vc < voff ic < ioff | Roff |
| otherwise | no change |
You may specify ON or OFF to indicate the initial state
of the switch when the controlling voltage is in the hysteresis
region.
The parameters ron and roff must have finite positive values.
| Voltage controlled switch | |
|---|---|
| vt | Threshold voltage. (Default = 0.) |
| vh | Hysteresis voltage. (Default = 0.) |
| von | On control voltage. (Default = vt + vh) |
| voff | Off control voltage. (Default = vt - vh) |
| ron | On resistance. (Default = 1.) |
| roff | Off resistance. (Default = 1e12) |
| Current controlled switch | |
|---|---|
| it | Threshold current. (Default = 0.) |
| ih | Hysteresis current. (Default = 0.) |
| ion | On control current. (Default = it + ih) |
| ioff | Off control current. (Default = it - ih) |
| ron | On resistance. (Default = 1.) |
| roff | Off resistance. (Default = 1e12) |
A change of state is considered to be an analog event. An input crossing a threshold is a “cross event”. Cross events will generate extra time steps so the switch timing is accurate.
A switch can be used anywhere in a circuit to improve timing accuracy by sensing cross events.
Switches also influence time step control as resistors, which control smoothness by curve fitting.
Switches are linear devices that do not iterate unless there is a state change.