### Engineering Note

```Engineering Note ILB, ILBB, IMC, ISC, IFC
Vishay Dale
Circuit Simulation of Surface Mount Inductors
INTRODUCTION
With the advent of higher component densities, smaller
components, and reduced design to market times, many of
today’s complex circuits are designed using a computer and
circuit simulation software rather actual physical bread
boarding.
SRF
Impedance
Inductors can be one of the most difficult passive
components to accurately simulate, due to their inherent
parasitic capacitive and resistive elements. These parasitic
elements are the result of the resistance and turn-to-turn
capacitance of the current conductor, which will affect the
characteristic impedance of the inductor, particularly at
higher frequencies. Figure 1 illustrates the equivalent circuit
model for a real inductor with parasitic elements.
100 000
10 000
Approx. 20 % SRF
Real
1000
Ideal
100
1
10
Frequency (MHz)
100
Figure 2. Impedance/Frequency Curves
of Real and Ideal 10 µH Inductor
R
C
R
L
C
L
Circuit A
Circuit B
Figure 1. Equivalent Circuit for a Real Inductor
Most inductors can be represented with an acceptable
degree of accuracy by one of the circuits shown in Figure 1.
Circuit A typically represents an inductor that uses a
magnetic core material such as ferrite or powdered iron.
Circuit B will accurately represent most nonmagnetic core
inductors commonly referred to as “air cores.” If the
equivalent circuit values of the parasitic capacitance and
resistance are known along with the effective inductance, the
inductor model can be inserted in the circuit simulator and
provide an accurate representation of the inductor’s true
performance in the A circuit.
Vishay Dale has generated the equivalent circuit values for
many of its surface mount product lines. A table illustrating
the equivalent circuit values for each of the current Vishay
Dale product lines follows this discussion.
SIMULATING THE PERFORMANCE OF AN
INDUCTOR
In many computer based circuit simulators, if a single
element inductor is placed in the circuit, it will be represented
as an ideal inductor. This may be acceptable if the simulation
is at a frequency well below the series resonant frequency
(SRF) of the inductor, as the impedance curve for the ideal
and the real inductors are identical over frequency until a
point that is about 20 % of the inductor’s SRF. At this point,
the impedance curves diverge due to the effects of the
parasitic elements.
However, the accuracy of the ideal inductor model will begin
to increase beyond 20 % of the inductor’s SRF.
Figure 2 is a graph of the impedance versus frequency
characteristics of a real and ideal inductor.
Document Number: 34098
Revision: 10-Aug-06
LIMITATIONS OF INDUCTOR MODELS
Most inductors are used well below their series resonant
frequency (SRF) and these basic, three element inductor
models will be very accurate under these simulation
conditions. The SRF of the inductor occurs when the
inductivereactance (XL) is equal to the capacitive reactance
(XC) of the conductor. The impedance of the inductor is at its
maximum and would be infinite if there were no core loss or
if the resistance of the conductor were zero. Above the SRF,
the XC exceeds XL and the inductor behaves like a capacitor.
As the frequency increases above the SRF point, the
inductor will go through several more resonant phases as a
result of secondary parasitic elements which require a more
complex equivalent circuit. For this reason, the typical useful
range for the three element inductor models is the SRF of the
For technical questions, contact: [email protected]
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183
Engineering Note ILB, ILBB, IMC, ISC, IFC
Vishay Dale
Circuit Simulation of Surface Mount Inductors and Impedance Beads
IMC-0402
EQUIVALENT CIRCUIT DATA
NOMINAL INDUCTANCE (nH)
CIRCUIT
RESISTANCE (Ω)
CAPACITANCE (pF)
INDUCTANCE (nH)
1.2
B
75.790
2.12680
0.896
1.5
B
50.568
1.48730
1.254
1.8
B
69.254
1.32050
1.469
2.2
B
72.762
0.91637
2.115
2.7
B
79.357
0.82001
2.356
3.3
B
87.174
0.66923
2.929
3.9
B
86.272
0.57138
3.452
4.7
B
123.660
0.47681
4.150
5.6
B
143.730
0.38200
5.255
6.8
B
171.930
0.31975
6.376
8.2
B
230.000
0.28377
7.329
10.0
B
213.970
0.23723
8.904
12.0
B
312.950
0.19187
11.175
18.0
B
554.440
0.13639
16.818
33.0
B
792.650
0.08367
30.769
39.0
B
1.059
0.07628
35.933
47.0
B
1.832
0.06090
45.300
56.0
B
1.987
0.05267
54.122
NOMINAL INDUCTANCE (nH)
CIRCUIT
RESISTANCE (mΩ)
CAPACITANCE (pF)
INDUCTANCE (nH)
1.5
B
0.0319
0.0000
1.34
1.8
B
0.0485
0.0000
1.65
2.2
B
0.0557
0.0000
1.98
2.7
B
0.0554
0.0125
2.52
3.3
B
0.0374
0.0118
3.15
3.9
B
0.0541
0.0232
3.68
4.7
B
0.0834
0.0362
4.40
5.6
B
0.1197
0.0439
5.46
6.8
B
0.1209
0.0486
6.54
8.2
B
0.1256
0.0515
7.82
10.0
B
0.1806
0.0555
9.64
12.0
B
0.2173
0.0620
11.55
15.0
B
0.2812
0.0630
14.64
18.0
B
0.3140
0.0647
17.45
22.0
B
0.3322
0.0698
21.26
27.0
B
0.4009
0.0683
25.98
33.0
B
0.5273
0.0740
31.95
39.0
B
0.5809
0.0694
37.29
47.0
B
0.7227
0.0723
45.30
56.0
B
0.9117
0.0667
53.70
68.0
B
1.0948
0.0717
63.19
82.0
B
1.4347
0.0684
76.62
100.0
B
1.5531
0.0709
93.26
IMC-0603
EQUIVALENT CIRCUIT DATA
www.vishay.com
184
For technical questions, contact: [email protected]
Document Number: 34098
Revision: 10-Aug-06
Engineering Note ILB, ILBB, IMC, ISC, IFC
Circuit Simulation of Surface Mount Inductors and Impedance Beads
Vishay Dale
IMC-0805-01
EQUIVALENT CIRCUIT DATA
NOMINAL INDUCTANCE (nH)
CIRCUIT
RESISTANCE (É¹)
CAPACITANCE (pF)
INDUCTANCE (nH)
3.9
B
0.0884
0.0075
4.3
4.7
B
0.0958
0.0061
4.6
5.6
B
0.1053
0.0325
5.5
6.8
B
0.1297
0.0320
5.2
8.2
B
0.1472
0.0398
8.1
10
B
0.1468
0.1445
11.2
12
B
0.1749
0.0598
12.6
15
B
0.1861
0.0836
16.4
18
B
0.2194
0.0698
18.8
22
B
0.2420
0.0837
22.4
27
B
0.2638
0.0921
27.4
33
B
0.2814
0.1046
33.4
39
B
0.3282
0.0924
39.0
47
B
0.3432
0.0975
45.3
56
B
0.4023
0.0927
55.7
68
B
0.4356
0.0936
67.9
82
B
0.4880
0.1503
79.8
100
B
0.5968
0.0968
94.4
120
B
0.7235
0.1994
97.7
150
B
1.1647
0.1295
132.9
180
B
1.2414
0.1698
150.2
220
B
1.3983
0.1719
194.2
270
A
17.7k
0.4812
230.6
330
A
16.4k
0.5637
274.2
390
A
12.6k
0.8714
331.9
470
A
10.5k
1.5701
425.7
560
A
10.9k
1.2488
491.0
680
A
12.1k
1.3662
592.1
820
A
13.5k
1.1962
737.5
1000
A
12.5k
1.4749
859.1
NOMINAL INDUCTANCE (µH)
CIRCUIT
RESISTANCE (Ω)
CAPACITANCE (pF)
INDUCTANCE (H)
0.010
B
89.79 m
0.0984
6.83 n
0.012
B
107.98 m
0.0965
9.09 n
0.015
B
119.35 m
0.1285
11.09 n
0.018
B
138.90 m
0.1390
14.62 n
0.022
B
135.92 m
0.1827
18.48 n
0.027
B
172.43 m
0.2258
22.37 n
0.033
B
218.71 m
0.1876
30.59 n
0.039
B
209.12 m
0.2440
35.42 n
0.047
B
215.71 m
0.2882
37.57 n
0.056
B
308.05 m
0.3251
46.38 n
0.068
B
224.86 m
0.3369
54.42 n
0.082
B
359.50 m
0.2936
63.2 n
IMC-1210
EQUIVALENT CIRCUIT DATA
Document Number: 34098
Revision: 10-Aug-06
For technical questions, contact: [email protected]
www.vishay.com
185
Engineering Note ILB, ILBB, IMC, ISC, IFC
Vishay Dale
Circuit Simulation of Surface Mount Inductors and Impedance Beads
IMC-1210
EQUIVALENT CIRCUIT DATA
NOMINAL INDUCTANCE (µH)
CIRCUIT
RESISTANCE (Ω)
CAPACITANCE (pF)
INDUCTANCE (H)
0.100
B
353.36 m
0.3709
80.52 n
0.120
B
363.80 m
0.5019
103.4 n
0.150
B
229.68 m
0.6020
139.55 n
0.180
B
312.54 m
0.6353
159.31 n
0.220
B
269.10 m
0.7814
205.23 n
0.270
A
5.98 k
0.6474
253.82 n
0.330
A
4.11 k
0.6869
309.87 n
0.390
A
4.59 k
0.7050
375.18 n
0.470
A
7.48 k
0.7929
439.72 n
0.560
A
9.09 k
0.9563
523.33 n
0.680
A
10.66 k
0.8764
646.61 n
0.820
A
11.24 k
0.7070
751.05 n
1.0
A
14.21 k
1.2100
0.99 µ
1.2
A
13.73 k
0.9900
1.15 µ
1.5
A
15.51 k
1.5800
1.46 µ
1.8
A
18.89 k
1.4300
1.72 µ
2.2
A
20.98 k
1.1200
2.11 µ
2.7
A
25.90 k
0.9800
2.66 µ
3.3
A
24.65 k
1.5200
3.16 µ
3.9
A
27.80 k
1.6900
3.67 µ
4.7
A
26.43 k
1.4100
4.5 µ
5.6
A
35.52 k
1.3400
5.28 µ
6.8
A
38.26 k
1.5700
6.32 µ
5.2
A
37.93 k
1.3500
7.52 µ
10.0
A
46.21 k
1.5200
9.43 µ
NOMINAL INDUCTANCE (µH)
CIRCUIT
RESISTANCE (Ω)
CAPACITANCE (pF)
INDUCTANCE (H)
0.010
0.012
0.015
0.018
0.022
0.027
0.033
0.039
0.047
0.056
0.068
0.082
0.100
0.10
0.12
0.15
0.18
0.22
0.27
B
B
B
B
B
B
B
B
B
B
B
B
B
A
A
A
A
A
A
64.1
88.7
130.7
143.7
200.2
156.7
273.4
197.6
212.7
277.6
314.1
325.6
412.8
11.46
13.69
13.69
18.45
28.14
45.62
0.1357
0.1463
0.1746
0.1926
0.1892
0.2227
0.1597
0.2976
0.2630
0.3289
0.2958
0.2483
0.3469
0.5351
0.4697
0.4757
0.5231
0.4544
0.4926
9.9 n
11.8 n
14.6 n
17.4 n
21.3 n
29.2 n
38.4 n
34.0 n
44.2 n
48.1 n
61.8 n
84.9 n
84.9 n
0.0935 µ
0.1177 µ
0.1424 µ
0.1623 µ
0.2012 µ
0.2408 µ
IMC-1210-100
EQUIVALENT CIRCUIT DATA
www.vishay.com
186
For technical questions, contact: [email protected]
Document Number: 34098
Revision: 10-Aug-06
Engineering Note ILB, ILBB, IMC, ISC, IFC
Circuit Simulation of Surface Mount Inductors and Impedance Beads
Vishay Dale
IMC-1812
EQUIVALENT CIRCUIT DATA
NOMINAL INDUCTANCE (µH)
CIRCUIT
RESISTANCE (kΩ)
CAPACITANCE (pF)
INDUCTANCE (µH)
0.33
A
28.00
0.5365
0.2957
0.39
A
29.24
0.5127
0.3429
0.47
A
29.47
0.5427
0.4508
0.56
A
41.36
0.4498
0.5104
0.68
A
32.51
0.4792
0.6067
0.82
A
32.76
0.4674
0.7412
1.00
A
12.40
1.6920
0.9513
1.20
A
12.33
1.6740
1.1640
1.50
A
14.92
1.6930
1.4020
1.80
A
18.89
1.4410
1.7370
2.20
A
23.51
1.6220
2.1300
NOMINAL IMPEDANCE
CIRCUIT
RESISTANCE (Ω)
CAPACITANCE (pF)
INDUCTANCE (µH)
40
A
65
0.900
0.0952
60
A
80
0.900
0.1533
68
A
100
0.900
0.1779
80
A
118
1.000
0.1993
120
A
157
1.200
0.3356
220
A
315
0.900
0.6037
300
A
420
0.800
0.7954
450
A
545
0.800
1.1186
600
A
690
0.800
1.4531
750
A
810
0.900
2.0182
1000
A
1.1k
0.658
2.4001
NOMINAL IMPEDANCE
CIRCUIT
RESISTANCE (Ω)
CAPACITANCE (pF)
INDUCTANCE (µH)
11
A
18
0.90
0.0273
32
A
50
0.85
0.1053
60
A
82
0.70
0.2114
90
A
125
1.00
0.2836
120
A
165
1.00
0.2969
150
A
208
1.00
0.4437
300
A
350
1.00
0.8621
400
A
510
0.90
1.3274
600
A
636
1.20
1.3454
1000
A
975
1.00
2.7573
1500
A
1600
1.00
4.7412
2000
A
2500
0.90
7.4365
ILBB-0603
EQUIVALENT CIRCUIT DATA
ILBB-0805
EQUIVALENT CIRCUIT DATA
Document Number: 34098
Revision: 10-Aug-06
For technical questions, contact: [email protected]
www.vishay.com
187
Engineering Note ILB, ILBB, IMC, ISC, IFC
Vishay Dale
Circuit Simulation of Surface Mount Inductors and Impedance Beads
ILB-1206
EQUIVALENT CIRCUIT DATA
NOMINAL IMPEDANCE
CIRCUIT
RESISTANCE (Ω)
CAPACITANCE (pF)
INDUCTANCE (H)
19
A
27
0.9
63.51 n
26
A
37
0.8
75.00 n
50
A
75
0.4
109.60 n
31
A
37
1.0
73.34 n
70
A
95
0.2
174.12 n
120
A
150
1.5
352.33 n
150
A
180
0.9
492.76 n
300
A
330
1.8
1.05 µ
500
A
485
2.1
1.69 µ
600
A
610
2.0
2.49 µ
NOMINAL INDUCTANCE
CIRCUIT
RESISTANCE (Ω)
CAPACITANCE (pF)
INDUCTANCE (µH)
0.010
A
1.04
0.1003
0.00741
0.012
A
1.21
0.1051
0.00782
0.015
A
1.80
0.2178
0.01284
0.018
A
2.50
0.2487
0.01564
0.022
A
2.35
0.2434
0.01889
0.027
A
3.00
0.2279
0.02466
0.033
A
3.07
0.1983
0.03188
0.039
A
3.63
0.4437
0.03427
0.047
A
4.39
0.2873
0.03947
0.056
A
5.47
0.4233
0.04478
0.068
A
4.74
0.3259
0.06028
0.082
A
10.12
0.3506
0.07696
0.100
A
7.50
0.4130
0.08288
0.120
A
2.39
0.5536
0.12007
0.150
A
3.37
0.5382
0.14700
0.180
A
3.20
0.6848
0.16420
0.220
A
3.99
0.6573
0.22131
0.270
A
4.27
0.6229
0.25678
0.330
A
4.75
0.6377
0.31673
0.390
A
3.00
0.9118
0.39058
0.470
A
7.49
1.1016
0.44061
0.560
A
6.19
0.9598
0.50199
0.680
A
7.79
0.7370
0.62592
0.820
A
6.85
1.0187
0.80402
1.000
A
10.40
1.3400
0.98740
ISC-1210 0.10 µH - 1 µH
EQUIVALENT CIRCUIT DATA
IFC-0805/0603
Contact Factory for Current Data
www.vishay.com
188
For technical questions, contact: [email protected]
Document Number: 34098
Revision: 10-Aug-06
Engineering Note ILB, ILBB, IMC, ISC, IFC
Circuit Simulation of Surface Mount Inductors and Impedance Beads
Why is the equivalent circuit inductance less than the
nominal value of the inductor? For instance, the equivalent
circuit inductance listed for an IMC-1210 0.82 µH inductor is
only 0.74 µH.
The effective inductance of a component can be adversely
affected by the parasitic elements. Capacitance cancels out
some of the inductive reactance and reduces the effective
inductance of the device. Throughout a family of inductors,
wire size, core size, core material and number of turns will be
varied to achieve the proper inductance. The most efficient
inductors (with smallest parasitic element) have the lowest
number of turns, the largest wire and the optimum core
dimensions.
Since it is not economically feasible to have ideal core and
wire sizes for each inductance value in a series, some values
will have more significant parasitic elements that affect the
performance of the inductor. For example, one core and wire
size may be used for as many as 5 adjacent values in an
inductor series. The number of turns is varied to achieve the
higher inductance values. An inductor with more turns will
have more inter-winding capacitance so the highest inductor
with the same core and wire size will typically be more
affected by the winding capacitance than the lower values.
I would like to perform a Monte Carlo analysis that will
examine my circuit over the tolerance range of all my
components. How much can I expect the parasitic elements
to change due to manufacturing tolerances?
This is a tough question to answer.
Vishay Dale and other inductor manufacturers sell inductors
based on four major specifications:
Vishay Dale
I use “S” parameters in my circuit simulator. Are they
available for Vishay Dale inductors?
Because of the complexity of distributing “S” parameters for
all the inductor series, we have opted not to provide “S”
parameters for these products. As an alternative, most circuit
simulation programs will generate “S” parameters for a
simulated circuit. The equivalent circuit elements for the
Vishay Dale inductors can be entered as a separate circuit
into the simulator which can in turn generate a table or file of
“S” parameters for the inductor model.
I am interested in simulating the performance of a Vishay
Dale inductor that is not on the charts contained within this
application note. How can I get equivalent circuit information
for this inductor?
Vishay Dale will be adding equivalent circuit information for
other products as demand requires. If there is a specific
inductor you would like information on that has not been
published, we can normally supply this information within
one week of the request.
My circuit simulator already contains a library of inductive
components models from Vishay Dale and other vendor
products. How do I know if these are accurate models?
Some component libraries contain models that have been
empirically generated from catalog specifications, and so
these models may not accurately depict product
performance. To have full confidence in your library of
inductive component models, we strongly suggest that you
contact the vendor of your circuit simulator to determine the
source of the supplied inductor model data. All data included
here in our Application Note has been generated by testing
normally processed product and represents the typical
performance you can expect from the Vishay Dale product.
Inductance ± a percentage tolerance
Minimum Q at a specified frequency
Maximum DCR of the winding or conductor
Minimum SRF
In order to achieve these specifications, core size and material,
wire size, and number of turns can be varied. Due to
manufacturing tolerances on all of the inductor components,
wire size and/or number of turns may vary on the same value
across production lots. Varying the wire size and/or turns will
affect the values of the parasitic components, however, the
specified L, Q, DCR, and SRF will always be in tolerance.
Vishay Dale designs and manufactures inductors with
respect for the behavior of parasitic elements. Typically, the
basic tolerance of the purchased inductor (i.e., 10 µH ± 10 %)
can be applied to all the equivalent circuit elements in the
inductor model with good success.
Document Number: 34098
Revision: 10-Aug-06
For technical questions, contact: [email protected]
www.vishay.com
189
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