Resistor models in the Cadence Spectre There are 3 resistor models in the Cadence Spectre simulator, they are:

�� Two Terminal Resistor (resistor)

�� Physical Resistor (phy_res)

�� Diffusion Resistor Model (rdiff) The following information is derived from these sources: 1: "Affirma Spectre Circuit Simulator Reference", pp 386-393, 404-406, 410-414, Product Version 4.4.6, June 2000. 1999 Cadence Design Systems, Inc. All rights reserved. Printed in the United States of America. Cadence Design Systems, Inc. 2: "Affirma Spectre Circuit Simulator Device Model Equations", pp223-226, Product Version 4.4.6, February 2001 2001 Cadence Design Systems, Inc. All rights reserved. Printed in the United States of America. Cadence Design Systems, Inc. 3: "HSPICE/SPICE Interface & SPICE 2G6 Reference Manual", pp47-48, Product Version 4.4.6, October 2001. 1990-2001 Cadence Design Systems, Inc. All rights reserved. Printed in the United States of America. Cadence Design Systems, Inc.

1: Two Terminal Resistor (resistor) Description It is the normally used resistor model in Spectre. Such a component can be stated in the

following two ways:

without model: r1 (1 2) resistor r=1.2K m=2

with model: r1 (1 2) resmod l=8u w=1u

where, parameters r and m in the first statement, l and w in the second statement are

called as instance parameters.

If the instance value R(inst) is not given, use the default resistance R(model) in the

model definition. If R(model) is not given too, the R(inst) can be calculated by:

R(inst) = Rsh * L / (W - 2 * etch)

The nonlinearity of resistor is calculated by:

R(V) = R(inst) / (1 + c1 * V + c2 * V ^ 2 + ...).

where ck is the kth entry in the coefficient vector.

The value of the resistor as a function of the temperature is given by:

R(T) = R(tnom) * [1 + tc1 * (T - tnom) + tc2 * (T - tnom)^2]

where

T = trise(inst) + temp or T = trise(model) + temp

Sample Model Statement model resmod resistor rsh=150 l=2u w=2u etch=0.05u tc1=0.1 tnom=27 kf=1

where, rsh, l, w and etc are called as model parameters.

Instance parameters

r (�) Resistance. l (m) Resistor length. w (m) Resistor width. m=1 Multiplicity factor. scale=1 Scale factor. Resform Use the resistance form for this instance.

Default is yes if r<thresh. Possible values are no or yes.

tc1=0 1/C Linear temperature coefficient. tc2=0 C-2 Quadratic temperature coefficient. trise (C) Temperature rise from ambient. isnoisy=yes Should resistor generate noise. Possible

values are no or yes. Model parameters Resistance parameters r=����� Default resistance. rsh=����/sqr Sheet resistance. thresh=1.0e-3 ��� Resistances smaller than this will use the

resistance form as opposed to the standard conductance form.

Resistor Size Parameters l=��m Default resistor length. w=1e-6 m Default resistor width. etch=0 m Width narrowing due to etching per side. etchl=0 m Length narrowing due to etching per side. scaler=1 Resistance scaling factor. Temperature Effects Parameters tc1=0 1/C Linear temperature coefficient. tc2=0 C-2 Quadratic temperature coefficient. tnom (C) Parameters measurement temperature. Default

set by options. trise=0 C Default temperature rise from ambient. Nonlinearity Coefficients coeffs=[...] Vector of polynomial conductance coefficients.

Noise Model Parameters kf=0 Flicker (1/f) noise coefficient. af=2 Flicker (1/f) noise exponent. Note: some parameters have the same name in statements and model definitions. If both of them are given, the values appear at the instance statements have the priority.

2: Physical Resistor (phy_res) Description A physical resistor consists of a linear resistor (tied between t1 and t2) and two diodes

(tied between t1-t0 and t2-t0). It is shown in the following figure. The diodes are junction

diodes. Under normal operation, the two diodes are reverse biased, but the parameter

subtype can reverse the direction of the diodes. If you do not specify t0, ground is

assumed. The instance parameters always override model parameters. If you do not

specify the instance resistance value, it is calculated from the model parameters.

subtype = p

subtype = n

subtype = poly

Thermal noise =RkT4

HzA

Flicker noise =fIrKF AF )(

HzA

If R(inst) is not given and R(model) is given

R(inst) = R(model)

Otherwise, R(inst) = Rsh * (L - 2 * etchl) / (W - 2 * etch)

If the polynomial coefficients vector (coeffs=[c1 c2 ...]) is specified, the nonlinear

resistance is R(V) = R(inst) / (1 + c1 * V + c2 * V2 + ...)

where V = V(t1) - V(t2)

Here V is the controlling voltage across the resistor. It is also the controlling voltage

when the model parameter polyarg is set to diff. In this form, the physical resistor is symmetric with respect to V(t1) and V(t2). The branch current as a function of the applied

voltage is given by I(V) = (V / R(inst)) * (1 + 1/2 * c1 * V + 1/3 * c2 * V2 + ...)

where ck is the kth entry in the coefficient vector.

If the model parameter polyarg is set to sum, the controlling voltage is defined as Vsum = ( (V(t1) - V(t0)) + (V(t2) - V(t0)) )/2

Here, Vsum is the controlling voltage between the resistor and the substrate, t0. In this

case, the device becomes asymmetric with respect to V(t1) and V(t2). The branch

current as a function of the applied voltage for this case is given by I(V) = (V / R(inst)) * (1 + c1 * Vsum + c2 * Vsum2 + ...)

The large-signal conductance is given by G(V) = (1 + c1 * Vsum + c2 * Vsum2 + ...) / R(inst)

The resistance as a function of temperature is given by R(T) = R(tnom) * [1 + tc1 * (T - tnom) + tc2 * (T - tnom)2]

where T = trise(inst) + temp

if trise(inst) is not given

T = trise(model) + temp

If you do not specify the junction leakage current (is) and js is specified, the leakage

current is calculated from js and the device dimensions.

is = js * 0.5 * (L - 2 * etchl) * (W - 2 * etch)

If you specify the instance capacitance or the linear model capacitance, linear capacitors are used between t1-t0 and t2-t0. Otherwise, nonlinear junction capacitors are used and

the zerobias capacitance values are calculated from the model parameters.

If C(inst) is not given and C(model) is given,

C(inst) = C(model)

Otherwise,

C(inst) = 0.5*Cj *(L -2*etchlc)*(W -2*etchc)+Cjsw*(W+L-2*etchc-2*etchlc)

If the capacitance is nonlinear, the temperature model for the junction capacitance is

used. Otherwise, the following equation is used. C(T) = C(tnom) * [1 + tc1c * (T - tnom) + tc2c * (T - tnom)2].

Sample Instance Statement res1 (net9 vcc) resphy l=1e-3 w=2e-6

Sample Model Statement model resphy phy_res rsh=85 tc1=1.53e-3 tc2=4.67e-7 etch=0 cj=1.33e-3

cjsw=3.15e-10 tc1c=9.26e-4

Instance Parameters r (�) Resistance. c (F) Linear capacitance. l (m) Line length. w (m) Line width. region=normal Estimated operating region. Possible values

are normal or breakdown. tc1=0 1/C Linear temperature coefficient of resistor. tc2=0 C-2 Quadratic temperature coefficient of resistor. tc1c=0 1/C Linear temperature coefficient of linear

capacitor. tc2c=0 C-2 Quadratic temperature coefficient of linear

capacitor. trise (C) Temperature rise from ambient. m=1 Multiplicity factor. Model Parameters Substrate Type Parameters subtype=p Substrate type. Possible values are n p or

poly. Resistance Parameters r=��������Default resistance. rsh=�����/sqr Sheet resistance. minr=0.1�����Minimum resistance. coeffs=[...] Vector of polynomial conductance coefficients. polyarg=diff Polynomial model argument type. Possible

values are sum or diff. Temperature Effects Parameters tc1=0 1/C Linear temperature coefficient of resistor. tc2=0 C-2 Quadratic temperature coefficient of resistor. tc1c=0 C-2 Linear temperature coefficient of linear

capacitor. tc2c=0 C-2 Quadratic temperature coefficient of linear

capacitor. tnom (C) Parameters measurement temperature. Default

set by options. trise=0 C Temperature rise from ambient. Junction Diode Model Parameters is (A) Saturation current. js=0 A/m2 Saturation current density. n=1 Emission coefficient. eg=1.11 V Band gap. xti=3 Saturation current temperature exponent. imelt=`imaxA' Explosion current. diode is linearized beyond

this current to aid convergence. jmelt=`jmeltA/m'2 Explosion current density. diode is linearized

beyond this current to aid convergence. imax=1 A Maximum current. currents above this limit

generate a warning. jmax=1e8 A/m2 Maximum current density. currents above this

limit generate a warning. dskip=yes Use simple piece-wise linear model for diode

currents below 0.1*iabstol. Possible values are no or yes.

bvj=���V Junction reverse breakdown voltage. Junction Capacitance Model Parameters c=0 F Default linear capacitance. cj=0 F/m2 Zero-bias junction bottom capacitance density. cjsw=0 F/m Zero-bias junction sidewall capacitance

density. mj=1/2 Junction bottom grading coefficient. mjsw=1/3 Junction sidewall grading coefficient. pb=0.8 V Junction bottom built-in potential. pbsw=0.8 V Junction sidewall built-in potential. fc=0.5 Junction bottom capacitor forward-bias

threshold. fcsw=0.5 Junction sidewall capacitor forward-bias

threshold. tt=0 s Transit time. Device Size Parameters l=���m Default line length. w=1e-6 m Default line width. etch=0 m Narrowing due to etching. etchl=0 m Length reduction due to etching. etchc=etch m Narrowing due to etching for capacitances. etchlc=etchl m Length reduction due to etching for

capacitances. scaler=1 Resistance scaling factor. scalec=1 Capacitance scaling factor. Noise Model Parameters kf=0 Flicker (1/f) noise coefficient. af=1 Flicker (1/f) noise exponent.

3: Diffusion Resistor Model (rdiff) Description

The rdiff model is a diffusion resistor model, which accurately models the temperature, applied bias and back-bias dependencies of NWell, N+, and P+ resistors. It is described in the paper MODEL FOR DIFFUSION RESISTORS (NWell, N+, P+) USED IN CMOS IC DESIGNS by M.J.B.Bolt, FASELEC Process Development Group, PDG-93029, Modified 3rd May 1995. Sample Instance Statement r2 (1 2 0) rdsn l=9u w=2u nb=0 m=1 Sample Model Statement model rdsn rdiff level=1 tr=27 dta=0 rshr=2.5e3 wtol=0.22u rint=3.5u swvp=13.4u power=2 tcr1=1.5e-3 tcr2=1e-5 vpr=40 Instance Parameters l=1.0 scale m Drawn length of resistor. Must be greater than

zero. Scale set by option scale. w=1.0 scale m Drawn width of resistor. Must be greater than

zero. Scale set by option scale. nb=0.0 Number of bends in the resistor. Must be

greater than or equal to zero. m=1.0 Multiplicity factor. Must be greater than zero. Model Parameters level=1.0 Level of this model. Must be 1. tr (C) Reference temperature. Default set by option

tnom. tref (C) Alias of tr. Default set by option tnom. tnom (C) Alias of tr. Default set by option tnom. dta=0 K Temperature offset of the device. trise=0 K Alias of dta. rshr=1.0e+3 �/sqr Sheet resistance at reference temperature.

Must be greater than zero. wtol=0.0 m Offset between the drawn and effective resistor

width. tcr1=0.0 1/K Linear temperature coefficient of the resistor. tcr2=0.0 1/K2 Quadratic temperature coefficient of the

resistor. vpr=100.0 V Reference Pinch-off voltage. swvp=0.0 V/m Coefficient of the width dependence of vp. power=1.5 Voltage exponent. Must be greater than zero. vdr=1.0 V Diffusion voltage at reference temperature. rint=0.0 ��m Interface resistance at reference temperature. tcrint1=0.0 1/K Linear temperature coefficient of the interface

resistor.

4: SPICE resistor model in Cadence Cadence also has an interface with SPICE simulator. The resistor model of the SPICE

simulator in Cadence is a simple one as listed below.

General form RXXXXXXX N1 N2 VALUE <TC=TC1,<TC2>>

N1 and N2 are the two element nodes. VALUE is the resistance (in ohms) and may be

positive or negative but not zero. TC1 and TC2 are the (optional) temperature

coefficients; if not specified, zero is assumed for both. The value of the resistor as a

function of temperature is given by:

value(TEMP)=value(TNOM)*(1+TC1*(TEMP-TNOM)+TC2*(TEMP-TNOM)**2))

Examples R1 1 2 100

RC1 12 17 1K TC=0.001,0.015