SPICE Diode

SPICE-compatible diode

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  • Simscape / Electrical / Additional Components / SPICE Semiconductors

Description

The SPICE Diode block represents a SPICE-compatible diode.

SPICE, or Simulation Program with Integrated Circuit Emphasis, is a simulation tool for electronic circuits. You can convert some SPICE subcircuits into equivalent Simscape™ Electrical™ models using the Environment Parameters block and SPICE-compatible blocks from the Additional Components library. For more information, see subcircuit2ssc.

Equations

Variables for the SPICE Diode block equations include:

  • Variables that you define by specifying parameters for the SPICE Diode block. The visibility of some of the parameters depends on the value that you set for other parameters. For more information, see Parameters.

  • Geometry-adjusted variables, which depend on several values that you specify using parameters for the SPICE Diode block. For more information, see Geometry-Adjusted Variables.

  • Temperature, T, which is 300.15 K by default. You can use a different value by specifying parameters for the SPICE Diode block or by specifying parameters for both the SPICE Diode block and an Environment Parameters block. For more information, see Diode Temperature.

  • Temperature-dependent variables. For more information, see Temperature Dependence.

  • Minimal conductance, GMIN, which is 1e–12 1/Ohm by default. You can use a different value by specifying a parameter for an Environment Parameters block. For more information, see Minimal Conduction.

  • Thermal voltage, Vt. For more information, see Thermal Voltage.

Geometry-Adjusted Variables

Several variables in the equations for the SPICE diode model consider the geometry of the device that the block represents. These geometry-adjusted variables depend on variables that you define by specifying SPICE Diode block parameters. The geometry-adjusted variables depend on these variables:

  • AREA — Area of the device

  • SCALE — Number of parallel connected devices

  • The associated unadjusted variable

The table includes the geometry-adjusted variables and the defining equations.

VariableDescriptionEquation
CJOdGeometry-adjusted zero-bias junction capacitance

CJOd=CJO*AREA*SCALE

IBVdGeometry-adjusted reverse breakdown current

IBVd=IBV*AREA*SCALE

ISdGeometry-adjusted saturation current

ISd=IS*AREA*SCALE

RSdGeometry-adjusted series resistance

RSd=RSAREA*SCALE

Diode Temperature

You can use these options to define diode temperature, T:

  • Fixed temperature — The block uses a temperature that is independent from the circuit temperature when the Model temperature dependence using parameter in the Temperature settings of the Spice Diode block is set to Fixed temperature. For this model, the block sets T equal to TFIXED.

  • Device temperature — The block uses a temperature that depends on circuit temperature when the Model temperature dependence using parameter in the Temperature settings of the Spice Diode block is set to Device temperature. For this model, the block defines temperature as

    T=TC+TOFFSET

    Where:

    • TC is the circuit temperature.

      If there is no Environment Parameters block in the circuit, TC is equal to 300.15 K.

      If there is an Environment Parameters block in the circuit, TC is equal to the value that you specify for the Temperature parameter in the Spice settings of the Environment Parameters block. The default value for the Temperature parameter is 300.15 K.

    • TOFFSET is the offset local circuit temperature.

Minimal Conduction

Minimal conductance, GMIN, has a default value of 1e–12 1/Ohm. To specify a different value:

  1. If there is not an Environment Parameters block in the diode circuit, add one.

  2. In the Spice settings of the Environment Parameters block, specify the desired GMIN value for the GMIN parameter.

Thermal Voltage

Thermal voltage, Vt, is defined by the equation

Vt=Nk*Tq

Where:

  • N is the emission coefficient.

  • T is the diode temperature. For more information, see Diode Temperature.

  • k is the Boltzmann constant.

  • q is the elementary charge on an electron.

Current-Voltage Equations

This table shows the equations that define the relationship between the diode current, Id, and the diode voltage, Vd. As applicable, the model parameters are first adjusted for temperature. For more information, see Temperature Dependence.

Vd RangeId Equation

Vd>80*Vt

Id=ISd((VdVt79)e801)+Vd*GMIN

80*VtVd3*Vt

Id=ISd*(eVd/Vt1)+Vd*GMIN

3*Vt>VdBV

Id=ISd(1+27(Vd/Vt)3e3)+Vd*GMIN

Vd<BV

Id=IBVd*(e(BV+Vd)/Vt1)ISd*(1(3(e*BV)Vt)3)+Vd*GMIN

Where:

  • ISd is the geometry-adjusted saturation current. For more information, see Geometry-Adjusted Variables.

  • Vt is thermal voltage. For more information, see Thermal Voltage.

  • N is the emission coefficient.

  • q is the elementary charge on an electron.

  • k is the Boltzmann constant.

  • T is the diode temperature. For more information, see Diode Temperature.

  • GMIN is the diode minimum conductance. For more information, see Minimal Conduction.

  • BV is the reverse breakdown voltage.

Junction Charge Model

The table shows the equations that define the relationship between the diode charge Qd, and the diode voltage, Vd. As applicable, the model parameters are first adjusted for temperature. For more information, see Temperature Dependence.

Vd RangeQd Equation
Vd<FC*VJQd=TT*Id+CJOd*VJ*1(1VdVJ)1M1M
VdFC*VJQd=TT*Id+CJOd*(F1+F3*(Vd-FC*VJ)+(M2*VJ)*(Vd2-(FC*VJ)2)F2)

Where:

  • FC is the forward bias depletion capacitance coefficient.

  • VJ is the junction potential.

  • TT is the transit time.

  • CJOd is the geometry-adjusted zero-bias junction capacitance. For more information, see Geometry-Adjusted Variables.

  • M is the grading coefficient.

  • F1=VJ*(1-(1-FC)(1-M))/(1-M)

  • F2=(1-FC)(1+M)

  • F3=1-FC*(1+M)

Temperature Dependence

The relationship between the geometry-adjusted saturation current and the diode temperature is

ISd(T)=ISd*(T/TMEAS)XTIN*e(TTMEAS1)*EGVt

Where:

  • ISd is the geometry-adjusted saturation current. For more information, see Geometry-Adjusted Variables.

  • T is the diode temperature. For more information, see Diode Temperature.

  • TMEAS is the parameter extraction temperature.

  • XTI is the saturation current temperature exponent.

  • N is the emission coefficient.

  • EG is the activation energy.

  • Vt is thermal voltage. For more information, see Thermal Voltage.

The relationship between the junction potential and the diode temperature is

VJ(T)=VJ*(TTMEAS)-3*k*Tq*log(TTMEAS)-(TTMEAS)*EGTMEAS+EGT

Where:

  • VJ is the junction potential.

  • EGTMEAS is the activation energy for the temperature at which the diode parameters were measured. The defining equation is EGTMEAS=1.16eV-(7.02e-4*TMEAS2)/(TMEAS+1108).

  • EGT is the activation energy for the diode temperature. The defining equation is EGT=1.16eV-(7.02e-4*T2)/(T+1108).

The relationship between the geometry-adjusted diode zero-bias junction capacitance and the diode temperature is

CJOd(T) = CJOd*[1+M*(400e6*(T-TMEAS)-VJ(T)-VJVJ)]

Where:

  • CJOd is the geometry-adjusted zero-bias junction capacitance. For more information, see Geometry-Adjusted Variables.

  • M is the grading coefficient.

Assumptions and Limitations

  • The block does not support noise analysis.

  • The block applies initial conditions across junction capacitors and not across the block ports.

Ports

Conserving

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Electrical conserving port associated with positive voltage.

Electrical conserving port associated with negative voltage.

Parameters

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Main

Diode area. The value must be greater than 0.

Number of parallel diodes that the block represents. The value must be greater than 0.

Magnitude of the current that the ideal diode equation approaches asymptotically for very large reverse bias levels. The value must be greater than or equal to 0.

Series diode connection resistance. The value must be greater than or equal to 0.

Diode emission coefficient or ideality factor. The value must be greater than 0.

Junction Capacitance

Options for modeling the junction capacitance:

  • No — Do not include junction capacitance in the model.

  • Yes — Specify zero-bias junction capacitance, junction potential, grading coefficient, forward-bias depletion capacitance coefficient, and transit time.

Dependencies

Selecting Yes exposes related parameters.

Value of the capacitance placed in parallel with the exponential diode term. The value must be greater than or equal to 0.

Dependencies

This parameter is only visible when you select Yes for the Model junction capacitance parameter.

Junction potential, VJ. The value must be greater than 0.01 V.

Dependencies

This parameter is only visible when you select Yes for the Model junction capacitance parameter.

Grading coefficient, M. The value must be greater than 0 and less than 0.9.

Dependencies

This parameter is only visible when you select Yes for the Model junction capacitance parameter.

Fitting coefficient,, FC, that quantifies the decrease of the depletion capacitance with applied voltage. The value must be greater than or equal to 0 and less than 0.95.

Dependencies

This parameter is only visible when you select Yes for the Model junction capacitance parameter.

Transit time, TT, of the carriers that cause diffusion capacitance. The value must be greater than or equal to 0.

Dependencies

This parameter is only visible when you select Yes for the Model junction capacitance parameter.

Options for specifying initial conditions:

  • No — Do not specify an initial condition for the model.

  • Yes — Specify the initial diode voltage.

    Note

    The SPICE Diode block applies the initial diode voltage across the junction capacitors and not across the ports.

Dependencies

This parameter is only visible when you select Yes for the Model junction capacitance parameter.

Selecting Yes for this parameter exposes the Initial condition voltage, V0 parameter.

Diode voltage at the start of the simulation.

Note

The block applies the initial condition across the diode junction, so the initial condition is only effective when charge storage is included, that is, when one or both of the Zero-bias junction capacitance, CJO and Transit time, TT parameters are greater than zero.

Dependencies

This parameter is only visible when you select Yes for the Model junction capacitance and Yes for the Specify initial condition parameter.

Reverse Breakdown

Options for modeling reverse breakdown:

  • No — Do not model reverse breakdown.

  • Yes — Introduce a second exponential term to the diode I-V relationship, thereby modeling a rapid increase in conductance as the breakdown voltage is exceeded.

Dependencies

Selecting Yes for this parameter exposes related parameters.

If voltage drops below this value, the block models the rapid increase in conductance that occurs at diode breakdown. The value must be greater than or equal to 0.

Dependencies

This parameter is only visible when you select Yes for the Model reverse breakdown parameter.

Diode current that corresponds to the voltage specified for the Reverse breakdown voltage, BV parameter. The value must be greater than 0.

Dependencies

This parameter is only visible when you select Yes for the Model reverse breakdown parameter.

Temperature

Select one of these options for modeling the diode temperature dependence:

  • Device temperature — Use the device temperature to model temperature dependence.

  • Fixed temperature — Use a temperature that is independent of the circuit temperature to model temperature dependence.

For more information, see Diode Temperature.

Dependencies

Selecting Device temperature exposes the Offset local circuit temperature, TOFFSET parameter. Selecting Fixed temperature exposes the Fixed circuit temperature, TFIXED parameter.

Order of the exponential increase in the saturation current as temperature increases. The value must be greater than 0.

Diode activation energy. The value must be greater than or equal to 0.1 eV.

Diode simulation temperature. The value must be greater than 0 K.

Dependencies

This parameter is only visible when you select Fixed temperature for the Model temperature dependence using parameter.

Temperature at which the diode parameters are measured. The value must be greater than 0 K.

Amount by which the diode temperature differs from the circuit temperature.

Dependencies

This parameter is only visible when you select Device temperature for the Model temperature dependence using parameter.

Extended Capabilities

C/C++ Code Generation
Generate C and C++ code using MATLAB® Coder™.

Introduced in R2008a