How do I model a custom LED with TINA?

[DiTBho]

I am using DesignSoft TINA v8 to simulate a couple of circuits. Everything is fine, except its library only supports a few models for the LED component and none of these models looks fine because with 5V I need a low Current-Limiting Resistor  to turn the LED on.



LEDs are constant current devices with a predictable forward voltage drop based on the amount of current flowing through them.  These I-V current-voltage curves are available in the datasheet for specific LEDs. The CQX35 shows it nicely, so if you want to drive one of these LEDs with a forward voltage of 1.5V off a 5V power supply, you need something in that circuit to absorb the extra (5-1.5)V. The easiest way to absorb extra power in a circuit is to use a simple resistor.  You need to know the intended LED to define the resistor using V=IR, but the math is very straightforward once you determine your system parameters.  If you want to drive that 1.5V LED at 5mA, you need to absorb (5-1.5)V at 5mA in a resistor.  (5-1.5)V = 5mA * R.  Solving for R gives a resistor value of 700 ohm.

700 ohm looks ok, but it's definitively too small far from what I'd like to achieve with my simulations, since I would like to have 1K ohm, so I would like to model a different LED.

Unfortunately I can edit the properties of the component, but I am bit lost with too many parameters

Code: [Select]

#       Name    Parameter                    Units      Default Example  Area
1       IS      Saturation current             A         1e-14   1e-14    *
2       RS      Ohmic resistance               Ω         0       10       *
3       N       Emission coefficient           -         1       1.0
4       TT      Transit-time                   s         0       0.1ns
5       CJO     Zero-bias junction capacitance F         0       2pF      *
6       VJ      Junction potential             V         1       0.6
7       M       Grading coefficient            -         0.5     0.5
8       EG      Activation energy              eV        1.11    1.11 Si
                                                                 0.69 Sbd
                                                                 0.67 Ge
9       XTI     Saturation-current temperature exponent  3.0     3.0 jn
                                                                 2.0 Sbd
10      KF      Flicker noise coefficient      -         0
11      AF      Flicker noise exponent         -         1
12      FC      Coeff. for for.-bias dep. cap. formula   0.5
13      BV      Reverse breakdown voltage      V         ∞       40.0
14      IBV     Current at breakdown voltage   A         1.0e-3
15      TNOM    Parameter measurement temp.    °C   




I was expecting to find just two parameters: "If" and "Vf". There many more.

I haven't yet understood how to import a PSPICE model into TINA, I am not sure I can do it with version 8, I haven't enough budget to upgrade to v12.


Anyone has already tried to create a custom LED model for TINA? If so, let me know