Application Note

Light Emitting Diode

The SPICE Model of LEDs

Table of contents
1. Overview ......................................................................................... 2
2. SPICE ................................................................................................ 2
3. Nichia's SPICE Models ............................................................... 2
4. Parameters of a SPICE Model ................................................. 4
5. Precautions When Using Nichia’s LED Models...............10
6. Summary ......................................................................................11This document contains tentative information, Nichia may change the contents without notice.
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Application Note
1. Overview
Electronic devices have been becoming more and more multifunctional than ever before. As a result, thedevices need to incorporate more capable and complicated circuits. Circuit simulations are an effective
tool to reduce the time and cost to develop the products using these circuits; the importance of circuit
simulations has been increasing for electronic device manufacturers. To meet the increasing need andrequirements for circuit simulations, Nichia offers simulation models for its LEDs that can be used for
SPICE simulations. SPICE is an electronic circuit simulator.
This application note provides information and precautions for use of the SPICE models Nichia offers.

2. SPICESPICE stands for “Simulation Program with Integrated Circuit Emphasis”. This is a circuit simulator toLight Emitting Diodesimulate the electrical behavior of a circuit on a computer. With SPICE, electrical behavior including a basic
DC analysis, AC (transient) analysis, and noise analysis can be simulated by creating a circuit modelthrough a text command or a Graphical User Interface (GUI).
SPICE was originally developed at the University of California Berkeley (UCB). Since a free source code for
SPICE is available, many companies in the IT and electronics industries develop and sell their own modified
SPICE simulators. This makes SPICE the most commonly used circuit simulator among all those currently
available.

3. Nichia's SPICE Models
3.1 Characteristics that can be Simulated using Nichia's SPICE Models
Nichia offers simulation models for its LEDs in a diode-model format. Figure 1 shows an example of a
SPICE model Nichia offers. Among the characteristics of the LED that are provided in the FORWARD
CURRENT CHARACTERISTICS/TEMPERATURE CHARACTERISTICS section in the specification, the behaviorof the following two characteristics can be reproduced with a simulation that is performed using Nichia's
SPICE models:
1. Forward Characteristics: Forward Voltage vs. Forward Current at the junction temperature of 25°C
(see Figure 2 on the following page)
2. Temperature Characteristics: Junction temperature vs. Forward Voltage at the sorting current of the
LED (see Figure 3 on the following page)
Simulations using Nichia's SPICE models do not cover other characteristics including capacitancecharacteristics, reverse characteristics, AC (transient) characteristics, etc.

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Application Note

Light Emitting Diode***********************************************************Document No.:SE-KSExxxxxx*Date:10/14/2020*Part Number :xxxxxxxx*Spec Ref. :SE-KSExxxxxx*All Rights Reserved Copyright (c) Nichia Corporation 2020**********************************************************.model xxxxxxxx D+ IS=2.5939E-13+ N=4.0113+ RS=0.24229+ IKF=0+ EG=3+ XTI=25*$
NVSW219F
NVSW219F* 本特性は参考です。 * 本特性は参考です。
管理番号 No. STS-DA7-15330
All characteristics
shown
reference
only and are not guaranteed. 管理番号 No. STS-DA7-15330
All characteristics shown
are for reference
onlyareandforarenot guaranteed.

Figure 1. Example of a SPICE Model Nichia Offers* パルス駆動により測定しています。
* パルス駆動により測定しています。
followinggraphs show
the characteristics
measured in pulse mode.
The following graphs The
show
the characteristics
measuredin pulse mode.

順電流
Forward Current(mA)

2000

1500

1000

順電圧
Forward Voltage(V)

2500
2400

2500
2400
順電流
Forward Current(mA)

ジャンクション温度-順電圧特性
ジャンクション温度-順電圧特性
Junction
Temperature vsJunction Temperature
vs
TaVf
TaVf
Forward Voltage Forward Voltage
TJ =25°C
IFP=700mA
4.0
4.0

2000

1500

1000

0
2.0

2.5

0
2.0
3.0

3.0

2.5
3.5

3.0
4.0

3.5

IFP=700mA

3.5

3.0

2.5

2.5

700
500

700
500

3.5

順電圧
Forward Voltage(V)順電圧-順電流特性
順電圧-順電流特性
Forward Voltage vsForward Voltage vs
VfIf
VfIf
Forward Current Forward Current
TJ =25°C
3000
3000

2.0
4.0
-60 -30

順電圧
順電圧
Forward Voltage(V) Forward Voltage(V)02.0-60 90-30 120
0 150
30 18060
30 60

90 120 150 180

ジャンクション温度
ジャンクション温度
Junction Temperature(°C)
Junction Temperature(°C)

1Figure
2. Example of Forward Characteristicsジャンクション温度-相対光束特性
Figureジャンクション温度-相対光束特性
3. Example of Temperature Characteristics1
順電流-相対光束特性 順電流-相対光束特性
Forward Current vsForward Current vsLuminous
Flux
Relative Luminous Relative
Flux
IfIv
IfIv
TJ =25°C
3.5
3.5

3.2 Verification of Nichia's SPICE Models

Junction
Temperature vsJunction Temperature
vsLuminous
Flux
Relative Luminous Relative
Flux
TaIv
TJ =25°C
IFP=700mA
1.4
1.4

TaIv

IFP=700mA

1.2

相対光束(T J =25°Cで正規化)
Relative Luminous Flux(a.u.)(Normalized at T J =25°C)

相対光束(T J =25°Cで正規化)
Relative Luminous Flux(a.u.)(Normalized at T J =25°C)

相対光束 (IFP=700mAで正規化)
Relative Luminous Flux(a.u.)(Normalized at IFP= 700mA)

相対光束 (IFP=700mAで正規化)
Relative Luminous Flux(a.u.)(Normalized at IFP= 700mA)

3.0 2 to verify that Nichia's SPICE models are correctly implemented for the
Nichia uses3.0OrCAD PSPICE
1.2

simulator. The
values of the model may be used for another simulator if it is a modified
2.5
2.5 same parameterversion of UCB
SPICE; notethat the simulation results
may be 1.0
different depending on the simulation
1.0
2.0
2.0
conditions.

1.5

1.5

0.8
0.8
The reproducibility of the characteristics verified at Nichia
is only for
Forward Voltage vs. Forward Current

1.0
and Junction
temperature1.0vs. Forward Voltage.

0.6

0.6

0.5

0.5
0.0
0

500

0.0
0.4
0 2000500 2500
1000 3000
1500 2000 2500 3000
1000 1500-60 -3000.4-60 90-30 120
0 150
30 18060
30 60

90 120 150 180

順電流
順電流
ジャンクション温度
ジャンクション温度
1
Current(mA)
ForwardJunction Temperature(°C)
Excerpt from the specification
forCurrent(mA)
the NichiaForward
NVSW219F
LED as an example. Junction Temperature(°C)
2

OrCAD and PSPICE are trademarks of Cadence Design Systems, Inc. Nichia's verification is performed using OrCAD Ver. 9 or higher.

This document
contains tentative information, Nichia may change the contents without notice.
* 本特性は色温度2700K~4500K、演色性ランクR70に対応しています。
* 本特性は色温度2700K~4500K、演色性ランクR70に対応しています。
Thethegraphsabove show
characteristics
forLEDs
2700K~4500K,
R70 LEDs of this product.
The graphs above show
characteristics
forthe2700K~4500K,
R70
of this product.

3/12

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Application Note
4. Parameters of a SPICE Model
Table 1 provides a list of parameters that are used for a typical diode model for a SPICE simulation. Six ofthese parameters (i.e. IS, N, RS, IKF, EG, and XTI) are supported by Nichia's SPICE models; with these six
parameters, the forward (DC) and temperature characteristics are reproduced. The other parameters are
not supported; note that they are not provided in the model file Nichia offers.
This section provides the information of the parameters and how to determine the values.
Table 1. Parameters Used for a Typical Diode Model
Characteristics

Light Emitting Diode

Forward(DC)

Parameter
Name

Parameter

Supported by
Nichia's Model

IS

Saturation Current

Supported

N

Emission Coefficient

Supported

RS

Parasitic Resistance(Series Resistance)

Supported

IKF

High-injection Knee Current

Supported

EG

Energy Gap

Supported

XTI“IS” Temperature Exponent

Supported

CJO

Zero-bias Junction Capacitance

UnsupportedM

Junction Grading Coefficient

Unsupported

VJ

Junction Potential

Unsupported

ISR

Recombination Current

Unsupported

ReverseNR

Emission Coefficient for ISR

Unsupported

(DC)

BV

Reverse Breakdown Voltage

Unsupported

IBV

Reverse Breakdown Current

Unsupported

TT

Transit Time

Unsupported

Temperature

Capacitance

Reverse(AC)

4.1 Parameters for the Forward (DC) Characteristics
The IS, N, RS, and IKF parameters are used to reproduce the forward characteristics of voltage vs. current.
These parameters express electrical characteristics of typical diodes. For Nichia's SPICE models, Nichia
determines the values of the parameters with an emphasis on how well the forward characteristics can be
reproduced.

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Application Note
4.1.1 IS: Saturation Current
The IS is the saturation current that flows in the reverse direction (i.e. negative voltage). In a simulation
with a typical diode model, the larger the IS is, the larger the current flowing in the reverse direction willbe (see Figure 4). This affects the forward voltage rise (i.e. the voltage at which the current starts to flow);
the larger the IS is, the lower the voltage rise will be. The same behavior is seen in the operating range ofan LED (See Figure 5); the forward voltage rise is reproduced with parameter IS in a simulation.

3

1.5E-11
IS: Small
IS: Large

IS: Medium
IS: Large

2

[A]

[A]

1E-11

IS: Small

2.5

IS: Medium

5E-12

1.5
1

0.5
0

-5E-12
-1

-0.5

0

2.5

0.5

2.7

2.9

3.1

3.3

[V]

[V]

Figure 4. Examples of the Characteristics

Figure 5. Examples of the Characteristics

of a diodeof an LED

4.1.2 N: Emission Coefficient
The N represents how many injected carriers recombine. For a SPICE model for a typical diode, the valueof parameter N is between 1 and 2. If the value is close to 1, that means the amount of recombination issmall; the closer the N is to 1, the more ideal the diode is, regarding the electrical characteristics. Figure 6
shows that the larger the N is, the larger the forward voltage will be. This behavior is also seen for LEDs;
the value of parameter N affects the forward voltage (see Figure 7). Since the forward voltage of an LED
is higher than that of a typical diode, the value of the N may be larger than 2 for an LED model.

3100
N: Small10

N: Small

2.5

N: Medium
N: Large

N: Medium

N: Large

2
[A]

1
[A]

Light Emitting Diode

0

0.1

1.5
1

0.01

0.5

0

0.001
0

0.5

1

1.5

2

2.5

2.7

Figure 6. Examples of the Characteristics
of a diode

2.9

3.1

3.3

[V]

[V]

Figure 7. Examples of the Characteristics
of an LED

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Application Note
4.1.3 RS: Parasitic Resistance (Series Resistance)
The RS is the resistive component connected to a diode (e.g. LED) in series. For a typical LED, the bonding
materials, and other connecting components (e.g. wire) are components that would be considered theresistive component. The larger the RS is, the less current will flow through the LED (See Figures 8 and 9);
the slopes in the high current regions change depending on the value of parameter RS.

100

3
RS: Small10

RS: Medium

2.5

RS: Large

2
[A]

[A]

1
0.1

RS: Medium
RS: Large

1.5
1

0.01

0.5

0.001

0

0

0.5

1

1.5

2

2.5

2.7

[V]

2.9

3.1

3.3

[V]

Figure 8. Examples of the Characteristics

Figure 9. Examples of the Characteristics

of a diodeof an LED

4.1.4 IKF: High-injection Knee Current
The IKF is the knee current when the current flowing into a diode is large. The IKF is used for common
SPICE simulators including PSPICE, though it is not included in UCB's diode model. This parameter is used
to change the slope of the forward characteristics at a certain point; the larger the IKF is, the higher thecurrent at which the slope changes will be (see Figures 10 and 11).
In the current range that is specified for the actual use of a diode, the characteristics will be close to those
at IKF=0 since the slope changes at a higher current as the IKF becomes larger.

3

100
IKF=0
10

IKF=0

2.5

IKF: Medium
IKF: Large

IKF: Medium
IKF: Large

2
[A]

1
[A]

Light Emitting Diode

RS: Small

0.1

1.5

1

0.01

0.5
0

0.001
0

0.5

1

1.5

2

2.5

2.7

2.9

3.1

3.3

[V]

[V]

Figure 10. Examples of the Characteristics

Figure 11. Examples of the Characteristics

of a diodeof an LED

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Application Note
4.2 Parameters for the Temperature Characteristics
The EG and XTI parameters are used to reproduce the temperature characteristics of the junction
temperature vs. voltage. Nichia determines the values of the parameters assuming the junction
temperature of the LED will be ≥25˚C during operation; there may be a large error in the reproducibilityof the characteristics when the junction temperature is much lower than 25˚C.

4.2.1 EG: Energy Gap
The EG parameter is the energy gap in the band structure of a typical semiconductor (i.e. band gap). Eachmaterial within a semiconductor has its own value for this parameter (e.g. Si=1.11eV); usually, this value
is used for a SPICE simulation. Nichia determines the value of parameter EG with an emphasis on how well

4.2.2 XTI: IS Temperature Exponent
The Parameter XTI is the temperature exponent of parameter IS; the value of the IS is determined in orderto reproduce the forward characteristics. The XTI affects how much the IS changes when the junction
temperature changes; the larger the XTI is, the smaller the slope of the temperature characteristics will be(i.e. the graph will have a downward slope. See Figure 12). Since Nichia's SPICE models are created usinga reference junction temperature of 25˚C, the base point where the slope will change is 25˚C. The basepoint for voltage differs depending on the values of parameters IS, N, RS, and IKF.

4

3.5

XTI: Small
XTI: Medium
XTI: Large[V]

Light Emitting Diodethe temperature characteristics can be reproduced.

3

2.5-60 -40 -20

020 40 60 80 100 120 140 160[°]

Figure 12. Examples of the Characteristics of an LED

4.3 Parameters for the Capacitance Characteristics
Diodes (e.g. LED) have capacitive components that act as capacitors. Unlike common capacitors, thecapacitance value of a capacitive component changes depending on the value of the voltage that is
applied to the diode. To reproduce those voltage-capacitance characteristics, parameters CJO, M, and VJ
are used.

4.3.1 CJO: Zero-bias Junction Capacitance
The CJO is the value of the junction capacitance at zero-bias (i.e. where voltage is not applied to the diodeand there is no current flowing through the diode).

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Application Note
4.3.2 M: Junction Grading Coefficient
The M parameter is the junction grading coefficient. If the impurity concentration in the depletion layerchanges abruptly at the p-n junction, the junction is called a step-graded junction; if the change is gradual,
the junction is called a linearly-graded junction. The slope of the voltage-capacitance characteristics canbe changed by changing the value of parameter M. Usually, the value of the M is determined to be
between the step-graded junction (M=1/2) and the linearly-graded junction (M=1/3).

4.3.3 VJ: Junction Potential
The VJ parameter is the junction potential. This is the potential difference in the depletion layer whenvoltage is not applied to the diode. Usually, the value of parameter VJ is determined depending on theLight Emitting Diodematerial within a semiconductor.

4.4 Parameters for the Reverse (DC) Characteristics
The ISR, NR, BV, and IBV parameters are used to reproduce the DC characteristics in the reverse direction
including the reverse leakage current and breakdown phenomenon (i.e. a phenomenon where the reverse
current starts to flow rapidly at a certain voltage when a high voltage is applied in the reverse direction).
If a protection device (e.g. Zener diode) is incorporated in an LED, the reverse characteristics of the LED
are affected by the forward characteristics of the protection device (see Figure 13); the reverse
characteristics of LEDs with a protection device may be greatly different from those of LEDs without aprotection device.
Forward Current
Reverse Current

A

A

K

K

LED without a Protection Device

LED with a Protection Device

Figure 13. Reverse Characteristics of an LED

4.4.1 ISR: Recombination Current
The ISR is the recombination current. With this parameter, the reverse leak current can be reproduced.
The value of parameter ISR needs to be determined at the same time as the value of parameter IS since
the forward characteristics are greatly affected by the recombination current when the current is low.

4.4.2 NR: Emission coefficient for ISR
The NR is the coefficient that is used to change the effect of parameter ISR.

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Application Note
4.4.3 BV: Reverse Breakdown Voltage
The BV is the value of the voltage at which the breakdown phenomenon occurs. For LEDs that have an
incorporated protection device, the reverse current starts to flow at a lower voltage compared to a typicalbreakdown phenomenon since the reverse breakdown voltage is dependent on the forward characteristicsof the protection device.

4.4.4 IBV: Reverse Breakdown Current
The IBV is the value of the reverse current that flows at the reverse breakdown voltage (i.e. BV).

4.5 Parameters for the Reverse (AC) Characteristics
The parameter TT is used to reproduce the AC (transient) characteristics in the reverse direction. As with

Light Emitting Diodethe reverse (DC) characteristics, the reverse (AC) characteristics are affected by an incorporated protection
device.

4.5.1 TT: Transit TimeThe TT is the transient time. When the operating direction is switched from forward to the reverse direction,
the accumulated carriers are transferred (diffused) to the reverse direction and the current flows in thereverse direction. The current flow stops when the carrier concentration decreases. See Figure 14.
Parameter TT indicates the amount of time from the moment of switching to the reverse direction until
the stop of the reverse current flow. The shorter the transient time is, the better the response
characteristics of the diode is.

I
TT
Time

Figure 14. Example Current Waveform of Transit Time

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Application Note
5. Precautions When Using Nichia’s LED Models‧

The SPICE models Nichia offers are not guaranteed to reproduce the characteristics of the LED when
it is used in the chosen application. Also, note that the characteristics may not be reproduced perfectly
and there may be errors between the characteristics reproduced and the characteristics seen during
actual use. Use the simulation results only as reference; sufficient verification must be done to ensure
there are no issues for the chosen application.

‧

Nichia’s models are to reproduce only the forward characteristics (Forward Current vs. Forward
Voltage) and temperature characteristics (Junction Temperature vs. Forward Voltage). The othercharacteristics including capacitance characteristics, reverse characteristics, transient characteristics
are not supported.

Light Emitting Diode‧The characteristics that are reproduced with Nichia’s models are the typical characteristics that areprovided in the Initial Electrical/Optical Characteristics section of the specification of the LED;
variations of each individual LED, characteristics ranks, etc. are not considered.

‧

Nichia’s models are created assuming the LEDs are used at the junction temperature of ≥25˚C; there
may be a large error in the reproducibility of the characteristics when the simulation is performed ata lower junction temperature.

‧

The junction temperature of an LED depends on the heat dissipation design and/or the operating
conditions of the chosen application. Regarding how to measure the junction temperature, refer tothe applicable specification and application notes.

‧

When the simulation is performed at a low current, the reproduced characteristics tend to be greatly
different from those during actual use; Nichia recommends performing a simulation at a current thatis ≥10% of the sorting current.

‧

For some parameters, a specific value is given to each material and/or the structure of the diode fora SPICE simulation. Nichia’s models are created with an emphasis on how well the characteristics canbe reproduced; the parameter values used for Nichia’s models may be different from the typical value
for each material/structure.

‧

Nichia has verified that Nichia’s SPICE models work properly with the OrCAD PSPICE simulator; Nichia
does not perform verifications with other simulators.

‧

Nichia provides a parameter file only; a symbol file for a circuit diagram is not included. Create asymbol file for the LED that is suitable for the simulator being used.

‧

Nichia provides the parameter files in text format (.txt). Convert them to a file format that is acceptedby the simulator being used or feed the simulator with another diode model and then overwrite thedata with Nichia’s parameters if necessary.

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Application Note‧

In the parameter file Nichia offers (see Figure 1), the lines starting with an asterisk (*) are for
information Nichia uses to control the file; these lines are not used for the simulations.

6. Summary
Nichia’s SPICE models may not perfectly reproduce the characteristics of the LED and may include errors.
In addition, there may be variations for each individual LED and/or the measurement repeatability/reproducibility and if these errors and variations affect the simulation, it may lead to a large difference
between the characteristics measured in the chosen application and the characteristics reproduced during
the simulation. Use the simulation results only as reference; perform a verification with the chosenLight Emitting Diodeapplication to ensure that the designed performance is achieved.

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Application Note

Light Emitting Diode

Disclaimer
This application note is a controlled document of Nichia Corporation (Nichia) published toprovide technical information/data for reference purposes only. By using this applicationnote, the user agrees to the following: This application note has been prepared solely for reference on the subject matters
incorporated within it and Nichia makes no guarantee that customers will see the same
results for their chosen application.
 The information/data contained herein are only typical examples of performances and/or
applications for the product. Nichia does not provide any guarantees or grant any licenseunder or immunity from any intellectual property rights or other rights held by Nichia or
third parties.
 Nichia makes no representation or warranty, express or implied, as to the accuracy,completeness or usefulness of any information contained herein. In addition, Nichia shallnot be liable for any damages or losses arising out of exploiting, using, or downloadingor otherwise this document, or any other acts associated with this document.
 The content of this application note may be changed without any prior or subsequent
notice.
 Copyrights and all other rights regarding the content of this document are reserved by
Nichia or the right holders who have permitted Nichia to use the content. Without priorwritten consent of Nichia, republication, reproduction, and/or redistribution of thecontent of this document in any form or by any means, whether in whole or in part,
including modifications or derivative works hereof, is strictly prohibited.

491 Oka, Kaminaka-Cho, Anan-Shi,
TOKUSHIMA 774-8601, JAPAN
Phone: +81-884-22-2311 Fax: +81-884-21-0148

NICHIA CORPORATION
http://www.nichia.co.jp

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