Current Controlled Switch

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Netlist Entry

Wxxx nout+ nout- vc model
nout+ Positive output node
nout- Negative output node
vc Controlling device

modelname 		Name of model. Must begin with a letter but can contain any character except whitespace and period '.'.
ic Initial condition. Hysteresis mode only. Defines initial state of switch if control voltage is between upper and lower thresholds. 0 for 'OFF' 1 for 'ON'

The controlling device can be any native (i.e. non-subcircuit) device in the circuit. The current used will be the current flowing into its first terminal. The first terminal is the one that is first in the device's netlist entry. Note that if the device is not a voltage source or implemented as a voltage source, the current is sensed by placing a zero-volt voltage source in series with the sensing device. This is done automatically and no user action is required.

Current Controlled Switch Model Syntax

.model modelname ISWITCH ( parameters )

Current Controlled Switch Model Parameters

Name Description Units Default
RON On resistance ???MATH???\Omega???MATH??? 1
ROFF Off resistance ???MATH???\Omega???MATH??? Hysteresis mode: 1.0E12. Continuous mode: 1.0E6
ION Current at which switch begins to turn on. (continuous mode) I 1mA
IOFF Current at which switch begins to turn off. (continuous mode) I 0
IT If present enables hysteresis mode. Sets threshold current I 0
IH Hysteresis voltage. (hysteresis mode) I 0
TON On time. (hysteresis mode) s 1ns
TOFF Off time. (hysteresis mode) s 1n
TD Delay time. (hysteresis mode) s 0
TD_ON On delay. (hysteresis mode) s TD
TD_OFF Off delay. (hysteresis mode) s TD
TIMETOL Time tolerance. (hysteresis mode) s 10p

Current Controlled Switch Notes

The current controlled switch has two modes of operation:

  1. Continuous mode: Behaves like a current controlled resistor. Between ION and IOFF the resistance varies gradually following a cubic law as described with the following equation:

    where:

    ???MATH???R???MATH??? = ???MATH???1/exp(-Lm - Lr*factor*(1.5 - 2*factor*factor) )???MATH???

    ???MATH???factor???MATH??? = ???MATH???I_{control}-0.5???MATH???

    ???MATH???Lm???MATH??? = ???MATH???-0.5*ln(g_{on}*g_{off})???MATH???

    ???MATH???Lr???MATH??? = ???MATH???ln(g_{off}/g_{on})???MATH???

    ???MATH???I_{control}???MATH??? = ???MATH???I_{cntrl} >1.0: 1.0, I_{cntrl}<0.0: 0.0, I_{cntrl}???MATH???

    ???MATH???I_{cntrl}???MATH??? = ???MATH???(i_{in} -(ION+IOFF)/2)/(ION-IOFF)+0.5 ???MATH???

    ???MATH???g_{off}???MATH??? = ???MATH???ROFF<>0: 1/ROFF, ROFF=0: GMIN???MATH???

    ???MATH???g_{on}???MATH??? = ???MATH???RON<>0: 1/RON, RON=0: GMIN???MATH???

  2. Hysteresis mode: Switches in a controlled time with a hysteresis characteristic. This mode is enabled if the IT parameter is defined. The switch transitions to the on state when:

    ???MATH???I_{control} > IT+IH???MATH???

    and to the off state when:

    ???MATH???I_{control} < IT-IH???MATH???

    The transition will be delayed by TD and the transition time will be TON when changing from OFF state to ON state and TOFF when changing from ON state to OFF state.

    The transition will follow the same characteristic as continuous mode. That is, during the transition period the actual resistance of the switch will follow the continuous mode characteristic with the control current following a linear transition between ION and IOFF.

    Hysteresis mode is similar and usually compatible with what is known as short-transition mode in PSpice. The difference is that in short-transition mode, the switching time is uncontrolled whereas in SIMetrix hysteresis mode the transition time is controlled by the TON and TOFF parameters.

GMIN is a simulation parameter which defaults to 1.0E-12 but which can changed using the .OPTIONS statement.

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