The document describes a simplified SPICE behavioral model for simulating the behavior of fuses in circuits. The model allows users to set parameters like current rating, fuse factor, internal resistance, and normal melting value to simulate how long it takes a fuse to blow under different current conditions. Simulation results are presented demonstrating how fusing time varies based on steady direct current levels and different current waveforms providing the same peak current. Instructions are provided on installing the model libraries and symbols for use in SPICE simulations.

1. Fuse Simplified SPICE Behavioral Model All Rights Reserved Copyright (C) Bee Technologies Corporation 2011

2. Contents Benefit of the Model Model Feature Parameter Settings Fuse Specification (Example) Fusing Time vs. DC Current Fusing Time vs. Current Pattern Specific Fuse Model Library Files and Symbol Files Location Simulation Index All Rights Reserved Copyright (C) Bee Technologies Corporation 2011

3. 1. Benefit of the Model Easily create your own fuse models by setting a few parameters, that’s usually provided by the manufacturer’s datasheet. Enables circuit designer to safely test and optimize their circuit protection design, and to predict component and circuit stress under extreme conditions (e.g. at the fuse blow). The model is optimized to reduce the convergence error. All Rights Reserved Copyright (C) Bee Technologies Corporation 2011

4. 2. Model Feature The model accounts for: Current Rating Fuse Factor Internal Resistance Normal Melting I 2 t Enable the model to simulate fusing time (blow time) as a function of I 2 t. The model can be used for testing the blow time for the different current pattern. A one-shot switch, once fuse is opened it cannot be closed. All Rights Reserved Copyright (C) Bee Technologies Corporation 2011 Fig.1 Fusing Time vs. Fusing Current Characteristic

5. 3. Parameter Settings Irate = the current rating of fuse [A] FF = Fusing Factor, the ratio of the minimum fusing current (the current that fuse start to heat up) to Irate . (e.g. Irate =400mA and the minimum fusing current is 620mA then FF = 620m/400m = 1.55) Rint = internal resistance of fuse I2t = Normal Melting value [A 2 , seconds] From the fuse specification, the model is characterized by setting parameters Irate, FF, Rint and I2t. All Rights Reserved Copyright (C) Bee Technologies Corporation 2011 Model Parameters: Fig.2 Fuse model with default parameters IRATE = 400m FF = 1.55 RINT = 650m I2T = 0.024

6. 4. Fuse Specification (Example) Fig.3 Shows the complete setting of fuse model parameters by using data from the datasheet of CCF1N0.4 provided by KOA Speer Electronics, Inc. All Rights Reserved Copyright (C) Bee Technologies Corporation 2011 the minimum fusing current is 620mA, FF = 20m/400m = 1.55 IRATE = 400m FF = 1.55 RINT = 650m I2T = 0.024 Part No. Current Rating (mA) Internal R. max. (m  ) I 2 t (A 2 , seconds) CCF1N0.4 400 650 0.024

7. 5. Fusing Time vs. DC Current The simulation result shows the fusing times, t F , (the time that fuse blows) at the different fuse currents, I F . All Rights Reserved Copyright (C) Bee Technologies Corporation 2011 t F = 956.677usec. at I F = 5A t F = 5.9221msec. at I F = 2A t F = 23.7861msec. at I F = 1A Simulation Circuit *Analysis directives: .TRAN 0 1s 0 100u .STEP PARAM dc_current LIST 1, 2, 5 *Integration Method: trapezoidal Simulation Result

8. 5. Fusing Time vs. DC Current Graph shows the comparison result between the simulation result vs. the measurement data. The fusing current error (average from 0.001-10 sec.) = 4.9% All Rights Reserved Copyright (C) Bee Technologies Corporation 2011 Comparison Graph

9. 6 Fusing Time vs. Current Pattern The simulation result shows the fusing times, t F , (the time that fuse blows) for the same peak current but different in current patterns(waveforms). All Rights Reserved Copyright (C) Bee Technologies Corporation 2011 t F = 59.984msec. for sine wave t F = 150.041msec. for triangle wave Simulation Circuit Simulation Result .TRAN 0 0.2s 0 100u *Integration Method: trapezoidal

10. 7. Specific Fuse Model If the most accurate result is required, we could provide the specific model that optimized for each part number of fuse. The fusing current error (average from 0.001-10 sec.) will reduce from 4.9% (simplified model) to 0.4% (specific fuse model) All Rights Reserved Copyright (C) Bee Technologies Corporation 2011 Model of fuse part number CCF10.4, all parameters and function are already set Error reduce to 0.4% Comparison Graph

11. Library Files and Symbol Files Location All Rights Reserved Copyright (C) Bee Technologies Corporation 2011 … \Fuse_smpl C:\Program Files\LTC\LTspiceIV\lib\sub C:\Program Files\LTC\LTspiceIV\lib\sym Copy/Paste into Copy/Paste into Copy the library files (.lib) from the folder …\Fuse_smpl\.sub\, then paste into the folder C:\Program Files\LTC\LTspiceIV\lib\sub Copy the symbol files(.asy) from the folder …\Fuse_smpl\.asy\, then paste into the folder C:\Program Files\LTC\LTspiceIV\lib\sym

12. Simulation Index All Rights Reserved Copyright (C) Bee Technologies Corporation 2011 Simulations Folder name Fusing Time vs. DC Current.................................. Fusing Time vs. Current Pattern............................ DC Pattern