Capacitor model |
The model accepts, for compatibility with other simulation software, either C or CAP.
.MODEL <model name> C [model parameters] .MODEL <model name> CAP [model parameters] |
The capacitor model consists of process-related device data that allow the capacitance to be calculated from geometric information and to be corrected for temperature.
Parameter | Description | Default | Units |
C | Capacitance multiplier. | 1.0 | |
CJ | Junction bottom capacitance. | F/m^{2} | |
CJSW | Junction sidewall capacitance. | F/m | |
DEFW | Default device width. If width is not specified on device line, then it is taken from the default width given in the model. | 10^{-6} | m |
NARROW | Narrowing due to side etching. | 0.0 | m |
TC1 | Is the linear temperature coefficient and is sometimes given in data sheets as parts per million per °C. To convert ppm specs to TC1 divide by 1E6. | 0.0 | Ω/°C |
TC2 | Quadratic temperature coefficient. | 0.0 | Ω/°C² |
TNOM | Temperature at which the model parameters were measured. If this value is specified overrides the nominal TNOM value which is set in the options. | °C | |
TABS | Specifies the temperature at which the component operates. This value, if specified, takes precedence over the analysis temperature. | °C | |
TREL | Device temperature relative to current temperature. If this parameter is specified but not the parameter TABS then the current temperature of the component is equal to the current temperature plus TREL. | °C |
If the capacitance value is omitted from device line, then the capacitance may be calculated from the process information (CJ, CJSW and NARROW) in the model and the given length and width from the capacitor device. The semiconductor capacitor has a capacitance computed as:
CAP = CJ·(L-NARROW)(W-NARROW)+2·CJSW(L+W-2·NARROW)
After the nominal capacitance is calculated, it is adjusted for temperature:
C_{TEMP} = CAP · C · (1+TC1(TEMP-TNOM)+TC2(TEMP-TNOM)^{2})
.MODEL CMOD C ( TC1=0.001 TABS=50 )
.MODEL CSEMI C ( CJ = 100u CJSW = 1n )