14 watt dc-dc converter using iics

7/27/2019 14 Watt DC-DC Converter Using IICs

1/21A Y A G E O C O M P A N Y

14 Watt DC/DC Converter usingIntegrated Inductive Components

Application Note


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14Watt DC/DC Converter usingIntegrated Inductive Components

SummaryIn compact step down converters, bobbin cores are often used as outputinductor. A reference circuit has been modified in order to substitute abobbin core by a fully gapped IIC. This component is designed to carry

currents up to 7A at 300 kHz without saturating. The chosen componentis an IIC in 3F35 material with a 0.2 mm full gap. The winding has fiveturns designed on a PCB with 1.7 mm double tracks in order to reachthe required low DC resistance. 3F35 material has been selected due tothe switching frequency. For other requirements in switching applications,FERROXCUBEs Integrated Inductive Components are also available in otherpower materials such as 3C30, 3C96 and 3F4.Compared to the original component in the circuit, a bobbin core(Coiltronics UP4B-2R2), the IIC shows some distinct advantages withrespect to board area and build height.

This demo design shows that Integrated Inductive Components are verysuitable for use in modern high frequency DC/DC converters.

ContentsIntroduction 3IIC Features 3General product data 4Ferrite material characteristics 5Product characteristics 6Design of IIC inductors 8Demo board description 11

Circuit waveforms 13

Annex A- Magnetic radiation 14Annex B- Circuit schematic 17- PCB layout 18- Component list 19


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Fig. 1 DC convert er demo board w it h 2 IICs


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IntroductionTodays power designs demand lowprofile components but withstandinghigh power densities. IntegratedInductive Components (IIC) are idealfor DC-DC converter applications

due to their compact size andadvanced gap technology.

Its 4.4 mm maximum heightmake IICs attractive inductors toapply in DC-DC converters fornotebook computers, PC motherboards, battery to core converters,distributed power systems andportable electronics.

Gapped versions allow a veryaccurate and constant inductance upto high currents densities, and alsoreduce temperature influence.

The geometry of the IntegratedInductive Component (IIC) based ona magnetically closed path reducesthe incidence of unwanted radiationof the magnetic field. This radiation,which depends on the currentthrough the inductor, can affect

signals in nearby circuits and in othercomponents.

This application note shows theperformance of an IntegratedInductive Component (IIC) witha full gap in a step down DC-DCconverter. The configuration of thewindings (number of turns and PCBtracks) has a special design to keepits DC resistance low.

IIC Features

Low profil e component (max height 4.4 mm).

Leads bent in a so-called gull wing shape.

Handled by standard pick and place equipment.

Soldered together wit h ot her ICs by reflow.

Number of turns configurable on t he PCB.

200/400/1000/2000 kH z swit ching frequency

(different power materials available).

Other p ossible functions wit h ot her mat erials/configurations(e.g. 3E6 fo r common-mode choke).

Very low rad iat ed emission.

H igh saturat ion, high inductance and low power loss mat erials.


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0.1

14.4 0.2

4 0.08

2.7 0.2

7.2 0.15

10.45 max

4.38 max

0.3 max1.0 0.6 max

0.75 0.75

0.1

14.4 0.2

4 0.08

2.7 0.2

1.0 0.6 max

0.75 0.75

Fig.2 IIC10P-14/4 and IIC10-14/4 out line

General product data

General data

Lead frame material:

copper, plated with tin-lead alloy(SnPb 85/15)

Solder ability:- compatible with reflow soldering- IEC 68-2-58, part 2, test Ta,method 1

Moulding material:liquid crystal polymer (LCP), flameretardant in accordance withUL 94V-0

Isolation voltage:> 500 Vdc between leads andbetween leads and ferrite core

Isolation resistance:>100 M between leads

Estimated Rdc vs Inductance

0

10

20

30

40

50

60

0 2 4 6 8 10

Inductance (H)

Rdc ()

70 m - 2 layer PCB tracks

70 m - 1 layer PCB tracks

SYMBOL PARAMETER VALUE UNIT

(l/A) core factor (C1) 2.47 mm-1

Ve effective volume 338 mm3

le effective length 28.9 mm

Ae effective area 11.7 mm2

m mass 1.85 g


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SYMBOL CONDITIONS VALUE UNIT

i

25C; 10 kHz; 0.1 mT 1400 20%

a

100 C; 25 kHz;200 mT

2400

B 25 C; 10 kHz; 250 A/m100 C; 10 kHz; 250 A/m

450 370

mT

Pv

100 C; 400 kHz; 50 mT

100 C; 500 kHz; 50 mT100 C; 500 kHz; 100 mT

60

90 700

kW/m3

DC; 25 C 10 m

Tc 240 C

density 4750 kg/m3

SYMBOL CONDITIONS VALUE UNIT

i

25 C; 10 kHz; 0.1 mT 1200 20%

B 25 C; 10 kHz; 250 A/m100 C; 10 kHz; 250 A/m

380 210

mT

tan/i

25 C; 10 kHz; 0.1 mT25 C; 30 kHz; 0.1 mT

10x10-6 30x10-6

B

25 C; 10 kHz;

1.5 to 3 mT

1x10-3 kW/m3

DC; 25 C 0.1 mT

c 130 C

density 4900 kg/m3

1 10 102

10 4

f (MHz)

' ,s ''s

10 3

10 2

1010 1

3F35

0 100 200 400

8000

6000

2000

0

4000

300

a

B (mT)

3F3525

oC

100oC

5000

50 50 2500

150

1000

2000

3000

4000

i

T (C)

3F35

0 40 80

1200

900

300

0

600

120T (C)

Pv

(kW/m3)

3F35

f(kHz)

B(mT)

500 50

500 100

1000 30

^

102 103

10 3

10

H (A/m)

10 4

3F35

101

10 2

50 100 1000

500

0 500

100

200

300

400

500H (A/m)

B(mT)

3F35

25oC

100oC

25 50 250

500

0 150

100

200

300

400

250H (A/m)

B

(mT)

3E625 oC

100 oC

40000

50 50 2500

150

10000

20000

30000

i

T ( C)o

3E6

10 1 10

10 5

f (MHz)

' ,s ''s

10 4

10 3

1010 2

3E6

''s

2

1

's

102 103

10

B (mT)1 10

10 4

Pv(kW/m )3

3F35

10 2

10 3

500

kH

z

1MH

z

T = 100oC

102 103

10 4

H (A/m)

10 5

3E6

101

10 3

102

Ferrite material characteristics

3F35 specifications 3E6 specifications


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Product Characteristics

Inductance vs DC current on IIC10G-14/4-3F35

0

1

2

3

4

5

6

7

8

9

0 2 4 6 8 10 12

DC current (A)

Inductance(H)

5 TURNS

6 TURNS

10 TURNS

Inductance vs DC current on IIC10G-14/4-3F4

0

1

2

3

4

5

6

7

8

0 2 4 6 8 10 12

DC current (A)

Inductance(H)

5 TURNS

6 TURNS

10 TURNS

Inductance vs DC current on IIC10G-14/4-3C30

0

1

2

3

4

5

6

7

8

9

0 2 4 6 8 10 12

DC current (A)

Inductance(H)

5 TURNS

6 TURNS

10 TURNS

IIC10G-14/4-3F35 (full gap)

IIC10G-14/4-3F4 (full gap)

IIC10G-14/4-3C30 (full gap)


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Inductance vs DC current on IIC10P-14/4-3F35

1

10

100

0 1 2 3 4 5 6

DC current (A)

Inductance

(H)

5 TURNS

6 TURNS

10 TURNS

Inductance vs DC current on IIC10P-14/4-3F4

1

10

100

0 1 2 3 4 5 6

DC current (A)

Inductance

(H)

5 TURNS

6 TURNS

10 TURNS

Inductance vs DC current on IIC10P-14/4-3C30

1

10

100

0 1 2 3 4 5 6

DC current (A)

Inductance(H)

5 TURNS

6 TURNS

10 TURNS

IIC10P-14/4-3F4 (partial gap)

IIC10P-14/4-3C30 (partial gap)

IIC10P-14/4-3F35 (partial gap)


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OUTPUT INDUCTORFigure 3 shows the basic circuit of aDC-DC converter with associatedwaveforms. When the switch isclosed (transistor S conducts), thecurrent rises linearly and flowsthrough the inductor into thecapacitor and the load. During theON cycle, energy is transferredto the output and stored in theinductor. When the switch is opened(OFF cycle), the energy stored inthe inductor causes the current tocontinue to flow to the output viathe diode. The output voltage can becalculated as:

ii

s

ono DVV

T

tV ==

where ton

is the time while theswitch is conducting,T

sis one period

of the switching signal andDis theduty cycle.

The amount of energy stored in theinductor can be varied by controllingthe ON/OFF cycles.

+=

=

ton s

on

Ts

T

t

LL

s

L

s

avgL

dttidttiT

dttiT

I0

0

)(

)()(1

)(1

Looking at the current shape throughthe inductor in figure 3, the inductorripple current can be calculated as:

so

minLmaxLL TDL

ViiI )1()()( _=_=

The minimum practical inductor

value causes the circuit to operateat the edge of critical conduction,where the inductor current justtouches zero with every cycle atmaximum load. This choice is a trade-off between size and efficiency. Lowinductor values cause large ripplecurrents, resulting in the smallestcore size, but poor efficiency andhigh output noise.

Assuming that all of the ripplecomponent in i

Lflows through

the output capacitor it causes anadditional chargeQin the capacitorresulting in a peak to peak voltageripple V

oat the output.

C

TI

C

QV sLo

8

=

=

The switching frequency andoperating point (%ripple or LIR)determine the inductor value as

follows:

IDVL

Ic

Vi IoVo

Vi

0

Vo

VL

current flow

transistor conductingtransistor cut-off

0

0

0

Ic

ID

IL

S

L IL

load

closed openswitch

Vi Vo

Ic+ ID = IL

IL(av) = Io(av)

+

+

Fig. 3 Basic circuit of a DC-DC converter with associated waveforms.

)(

)1(

MAXos

o

ILIRf

DVL

_=

where D = Vo/Vi in continuous mode(current through the inductor isalways higher than zero).

Example:

Vi=24 V,V

o=2 V, I

o(MAX)=7A,

fs= 300 kHz, 50%ripple current

or LIR = 0.5.

HAkHz

VL 75.1

75.0300

)083.01(2=

_=

Maximum peak current through theinductor can be increased up to 7A.For that reason, DC resistance ofthe winding should be kept as low

as possible to prevent high windinglosses in the inductor.

dcdc RIP2=

The DC resistance of the windingcan be calculated from the crosssection and length of the coppertracks and are shown in the graphon page 4. Note that double tracksresults in half the DC resistance.

sl

Rdc =

Design of IIC inductors


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Example and recommended

PCB layout for IIC winding.

Io(MAX)

=7Anumber of turns = 5thickness of the PCB copper = 70m per layer

In this case the IIC should have 5turns. As the IIC has 10 leads, everytwo leads are connected in parallelwith solder pads to achieve 5 turns.

The windings are closed through thePCB tracks. To increase the coppercross section of the tracks and toreduce the DC resistance, the tracksare arranged in both top and bottomlayer of the PCB and connected

through vias (figure 4).

The width of every track is 1.7 mm(figure 5) and the thickness is 70 m.

The length of every track is 9.3 mmbut as there are tracks in two layersconnected with vias, the thicknesscan be considered as double (140m).

The total DC resistance is the sumof the resistance of the IIC leads, the

four doubled tracks and the eightvias plus soldering contacts.

)()()( contactsviasdctracksdcIICdcdc RRRR +++=

where

=

=

mmm

mmmmR

tracksdc

66.2

7.110702

3.910174

2-3

- 6

)(

To calculate the contribution of theIIC leads, the resistance of 1 lead(1.15 m) and the electrical circuit

must be taken into account. Theequivalent electrical circuit for thiscase (winding of five turns) is shownin figure 6.

double PCB tracksconnected by vias

Fig. 4 IIC on board (5 t urns).

Fig. 5 Recommended layout for 5

turns (top view).

R(1lead)

R(1lead)

1 2 3 4 5 6 7 8 9 10

11121314151617181920

Fig. 6 Equivalent electr ical cir cuit (5

turns).

To set up five turns, every two leadsare connected, so two resistorsare in parallel per turn. Turns areclosed through the PCB layout. TheDC resistance of the IIC leads canbe calculated as 5 times the parallelvalue of two leads:

( )

=

+

==

m

RRR leadleadIICdc

88.21015.11015.1

1015.11015.15

//5

-3-3

-3-3

)1()1()(

The total resistance of the outputinductor results in:

=++=

++= +mmmm

RRRR contactsviasdctracksdcIICdcdc

54.8366.288.2

)()()(

It was found empirically that theresistance caused by the eight viasand the soldering contacts is around3m

Now the maximum dissipated powercan be calculated as:

Pdc(max)

= (7A)2. 8.56m = 0.42W

For a fixed number of turns, theinductance can be calculated as:

L(nH)=AL . N2


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COMMON-MODE CHOKETo avoid conduction of switchingnoise from an SMPS to themains, an input filter is generallynecessary. Since the noise signalis mainly common mode, currentcompensation can be used to avoidsaturation. (Fig 7A)Differential currents cause fluxes thatcancel out, the impedance presentedby the choke is practically zero. Thisleaves the differential signal passingthrough the choke unattenuated.Common mode noise, however,causes common mode currents.

These current flows in the samedirection in the two windingscreating equal and in phase magnetic

fields. The choke shows highimpedance to the common modecurrent and causes attenuation.

To test the noise attenuated by thecommon mode choke a precisionspectrum analyser should be used.

That equipment gives noise readingsagainst frequency in dBV units.

=

V

VdBVNoise

1log20)( 10

The noise can be written in naturalunits (volts):

-620

)(

1010)(

=

dBVNoise

voltsV

Fig. 7 Equivalent circuit for a common

mode choke.

+

+

+ +_

_

_ _

winding 1

winding 2

flux generated by current 1

flux generated by current 2

Fig. 7A Flux cancell ing in a common

mode choke.


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The 14 W DC-DC converterdemo board demonstrates theperformance of the IIC as outputinductor and common mode choke.

This converter is intended to stepdown voltages from batteries and/orAC adapters, generating a precisionlow output voltage.

Most of the output inductors usedfor this kind of converters aredrum cores like UP4B-2R2 fromCoiltronics. IIC, having the sameelectrical performance as thesedrum cores shows some distinctadvantages.:

Benefits

from IIC

IIC DrumCore

Smaller area 14.5 mm x12.4 mm =179.8 mm2

26 mm x17 mm =442 mm2

Lower height 4.4 mm 7.87 mm

Repeatabilityofperformance

Leadsautomaticallyassembled.

Turns

arranged onPCB.

Turnsarrangedby hand.

Table 1 Benefits from IIC.

The output inductor is an IIC in3F35 with a 0.2 mm full gap. Thiscomponent withstands up to 7Aat 300 kHz without saturating. Thewinding has five turns designed on aPCB with 1.7 mm double tracks in

order to reach a low DC resistance.3F35 material has been selected dueto the switching frequency. For otherrequirements in switching frequency,different power material are like3C30, 3C96 or 3F4 are available.

A second IIC has been includedin the demo board. This is a non-gapped IIC in 3E6 material workingas common mode choke in thebattery line to filter the noise causedby the square wave switching signalsthat trigger the power MOSFETtransistors. It has two windingsof five turns each designed tocompensate current peaks that canaffect the battery line and also othercomponents. 3E6 and 3S4 are highimpedance materials recommendedfor this application.

This demo board is a fully assembledand tested circuit.

The 7A buck-regulator is optimizedfor 300 kHz and an output voltagesetting around 1.6 V.

The PC board layout deliberatelyincludes long output power andground buses in order to facilitatethe evaluation of the circuit and to

CONVERTER SPECIFICATION

Nominal output power 11 W

Maximum output power 14 W

Load current 5.5 A continuous (7 A peak)

Output voltage range 1.25 V to 2 V

Input voltage range 7 V to 24 V

Switching frequency 300 kHz

Efficiency 90 %(Vout =2 V, Vbatt =7 V, Iload =4 A)

Output voltage ripple 1.1%(Vou t=2 V, Vbatt =7 V, Iload =4 A)

Outline dimensions 150 mm x 86 mm

Table 2 Converter specification.

provide space for soldering differenttypes of output filter capacitors.In a commercial design the outlinedimensions of the board could bereduced to 33 mm x 33 mm x 6.5mm. With these dimensions, thepower density that could be achievedis1.50 W/cm3. Also note that theboard includes some componentslike switches and jumpers that areneeded to test the circuit in an easyway, but these components wouldnot be included in a real application,where the total area is reduced.

The components with the maximumheight are the output tantalumcapacitors. A typical drum core ishigher than these capacitors while

the IIC keeps the same height.

Demo board description


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Fig. 8 Qu ick start connecti on.

EQUIPMENT NEEDED 7 V to 24 V, >20 W power supply. DC bias power supply, 5 V/100 mA. Active load capable of sinking 7A. Digital multi meter. 100MHz dual-trace oscilloscope.

QUICK START

1. Connect the 5 V DC bias powersupply to the +5 V VBIAS andGND terminals.

2.Connect the 20 V power supply tothe battery line: VBATT MAX.

3.Connect the active load to theVOUT and GND terminals.

4.Ensure that the shunt is connectedat SW1 (SHDN\ = Vcc).

5.Turn on battery power prior to +5V bias power.

6. Do not change the DAC codewithout cycling +5 V bias power;otherwise, the output voltageramp will probably bump into the

over- or under voltage protectionthresholds and latch the circuit off.If this happens, just cycle power orpress the RESET button.

7. Set switch SW13 per Table 3 toget the desired output voltage.

D3 D2 D1 D0 OutputVoltage (V)

0 0 0 0 2.00

0 0 0 1 1.95

0 0 1 0 1.900 0 1 1 1.85

0 1 0 0 1.80

0 1 0 1 1.75

0 1 1 0 1.70

0 1 1 1 1.65

1 0 0 0 1.60

1 0 0 1 1.55

1 0 1 0 1.50

1 0 1 1 1.45

1 1 0 0 1.40

1 1 0 1 1.35

1 1 1 0 1.30

1 1 1 1 1.25

Table 3 Output voltage settings.

EFFICIENCY MEASUREMENTEfficiency measurements requiresmore careful instrumentation thanmight be expected. Do not use only

one digital multi meter.A common error is to move it fromone spot to another to measure thevarious input/output voltages andcurrents. This results in changingthe exact conditions applied to thecircuit due to series resistancesin the ammeters. Its better tomonitor VBATT, VOUT, IBATT and ILOADsimultaneously, using separate testleads directly connected to the inputand output board terminals.

The power consumed by the +5 Vbias supply must be included to makeefficiency calculations:

( ) ( )BIASBATTBATTLOADOUT

IVIV

IVEfficiency

5

=


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CIRCUIT WAVEFORMS

Gate drive for t op M OSFET D1 and lower M OSFET

D2 (Fig. 9)

PWM signals to drive the MOSFETs.Circuit conditions:Vout =2 V.Iout =3 A.Vbatt =8.6 V

Output voltage ripple. (Fig. 10)

AC content of the output voltage.Circuit conditions:Vout =2 V.Iout =3 A.

Vbatt =8.6 V.Vout ripple =23.8 mV.

The voltage ripple does not depend on the load currentsince the inductance value is constant.

Noise at t he batt ery line without common mode

choke. (Fig. 11)

Noise spectrum from DC to 1 MHz.

Circuit conditions:Vout =2 V.Iout =5 A.Vbatt =12 V.

Noise at the switching frequency (317.5 kHz): 42.83dBV

Noise at the bat ter y line including the common

mode choke. (Fig. 12)

Noise spectrum from DC to 1MHz.Circuit conditions:Vout =2 V.Iout =5 A.Vbatt =12 VNoise at the switching frequency (317.5 kHz): 37.32dBV. Noise is reduced to the half in natural units


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Magnetic radiationThe miniaturization trend hasresulted in smaller components andgreater board densities in electronicapplications. This very density,which packs components into

ever-smaller spaces, makes it moreimportant than ever to examine theeffectincluding possible damageeach component may have on signalsin nearby circuit paths and on othercomponents. This application noteexamines the way in which thegeometry of magnetic components,such as inductors or transformers,may affect the incidence of unwanted,low-frequency radiation of the

magnetic field. In the followingexperiment, commercially availableinductors are used as an outputchoke in a DC/DC converter.

Two types of inductors areused; bobbin cores which havemagnetically-open paths and anIntegrated Inductive Component(IIC) from FERROXCUBE with a fullgap and a magnetically closed path.

Magnetic pathThe electrical properties of magneticcomponents, such as transformersand inductors, are based on threemain parameters:

The winding that transforms theelectric current into a magneticfield

The magnetic properties of

the material, such as magneticpermeability, that determine themagnetic flux induced by themagnetic field.

The shape of the componentthat determines the path of themagnetic field.

The relationship between these3 parameters will determine thebasic properties of the magneticcomponent. With relatively simpleformulas, it is possible to calculatethe inductance, maximum current,and power loss of the inductor.

These are the most importantelectrical parameters needed todesign a component for a givenapplication. Also, the geometryof the component will influencethe radiation capability of the

magnetic component, a capabilityuninfluenced by any of the electricalparameters used in the design.For a clearer understanding of thecrucial role of geometry for radiatedemissions, magnetic componentscan be broken into two groups.First, in closed magnetic circuits,the magnetic flux remains insidethe magnetic core, and most of themagnetic-field lines are closed lines

surrounded by the winding. A goodexample of this first geometry is atoroid (Figure 1). Second, in openmagnetic circuits, the magnetic fluxflows briefly in the magnetic coreand then through the ambient air.Sometimes most of their length isnot within the magnetic core butpasses through the surroundings,

thereby crossing conductors orother components. An example

of the second geometry is a rod(Figure 1). In fact, there are manygeometric configurations that willlead to designs that radiate to agreater or lesser extent dependingon just how open they are. Theproducts examined in this article aretwo examples of the aforementionedgeometries and show similarelectrical properties.Inductance is about 5 H, DC-

resistance below 10 m, saturationcurrent of approximately 7 A for theIntegrated Inductive Component andapproximately 10 A for the bobbincore. They have similar volumes: theIIC is about 576 mm3, and the bobbincore is about 650 mm3 (Figure 2).

Fig. A1 Flux dist ribut ion in a t oroid (clo sed magnetic circuit ) where no

radiation can be noticed, and in a rod (open magnetic circuit) wit h radiation

leaving the p roduct.

Fig. A2 Int egrat ed inductive

Component (left ) and a bobbin core.

Annex A


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15Ferroxcube

Why is magneticradiation an issue?In many power applications, suchas power conversion, magneticcomponents are subjected to highcurrents and, consequently, to very

high magnetic fields. Depending onthe core geometry, magnetic fieldsmay radiate from the inductivedevice. Such fields are relativelystrong in the area near the magneticcomponents and will couple with anyconductor loop present on the PCBclose to the component.

This means that harmful switchingharmonics can appear anywhere

in the circuit, causing radiation,degrading the quality of digitalsignals, or even damaging sensitiveICs. Functionality may be the firstcriterion in choosing a component;but ultimately, the equipmentcontaining that component mustcomply with EMC regulations. Severalcommittees have set limits for bothconducted and radiated interference.In Europe, CISPR 16 sets forth themeasuring procedures/methods forsuch low frequency radiation (9 kHzto 30 MHz). Measurement specificsapplicable in the United States can befound in FCC, Part 15.

Test method andexperiments

This experiment relies on the so-called Van Veen method. 1) Usingthis method, the device-under-test

(DUT) is placed within a loopantenna two meters in diameter.This loop antenna is made of RG223/U coaxial cable with two slits (fittedwith a resistor networks) placedsymmetrically, each 90 from thecurrent probe. Figure 3 depicts theantenna setup. The current inducedin the loop is measured by a current

probe connected to a spectrumanalyzer and is expressed in dBA.In this test setup, the noise fromthe environment will be negligibleas compared to the currents fromthe DUT. To check the effect ofradiation, the DUT was connectedto an RF power amplifier, using a 100kHz square wave of 2.8 A amplitude.

The objective of this experiment

is to measure the radiation undersimilar conditions for both theopen magnetic circuit and theclosed magnetic circuit. Figure 4shows the radiation generated byboth components expressed indBA. These results confirm thatopen magnetic circuits have muchhigher radiation levels than closedcircuits. Note the amplitude of theharmonics. The difference between

the two components is 8 dBA at100 kHz (main frequency) and 6dBA at 300 kHz (third harmonic).Given these figures, it can be derivedthat the difference in radiation isalmost constant, independent of theamplitude of the signal. Consequently,the advantage of using closedmagnetic circuits holds in every case

even where radiation is relativelylow. The next experiment comparedthe inductors in a real application,a DC/DC converter, working as anoutput choke. The converter is astandard design and the operatingtest conditions were as follows: 2.3V output voltage delivering 2 A anda switching frequency of 600 kHz.

The results given in Figure 5 clearly

depict the advantage of using theintegrated inductive componentversus the drum core. When the IICis used, radiation levels stay withinthe radiation values of the overallsystem. In the case of the bobbincore spikes are measured at 600 and1800 kHz. A comparison betweenFigures 4 and 5 shows that theradiation of the DC/DC converter is5 dBA, in the frequencies unaffected

by the radiation of the inductors.

Fig. A3 Antenna loop used to carr y out H -field measurements in t he range

9 kHz to 30 M Hz. The current p robe translates the current in t he loop t o

voltage.

Annex A


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16Ferroxcube

ConclusionAt low frequencies, both conductedand radiated interference shouldbe taken into account. These designprinciples are necessitated not

just by regulatory limits but by the

demands for functionality and designintegrity in the completed system.Magnetic components with a closedmagnetic circuit design (e.g., anIntegrated Inductive Componentfrom FERROXCUBE) produce verylittle or negligible radiation. The useof IICs helps forestall such problemsas inducing currents on the tracks,currents that could damagecomponents, and currents that

might influence other signals. Theseclosed magnetic circuit devices are,therefore, well suited for use in anykind of equipment where othercircuits or PCBs might be affected bymagnetic radiation.

References1. Goedbloed, Jasper J.Electromagnetic Compatibility(CISPR Publication 15). IEC: Geneva,

Switzerland: 1992.

2. Ferroxcube Soft Ferrite andAccessories Handbook. 2002

0

10

20

30

40

50

60

100 200 300 400 500 6000

Freq. (kHz)

dBA drum core IIC

Fig. A4 Radiat ion on a dr um core and a IIC excit ed wit h a square wave:100 kH z, 2.9 Amps peak-peak. The square volt age becomes t riangular current

when passed across the induct ors. The main frequency and the third harmoni c

can be seen at 100 and 300 kH z.

0

5

10

15

20

25

30

35

600 1200 1800 24000

Freq. (kHz)

dBA

drum core IIC

Fig. A5 IIC and drum core working as out put choke on a DC/DC convert er.

IIC shows negligible radiat ion (comparabl e wit h t he noise generated by rest of

the circuit ry) while on the drum core, two harmoni cs can be seen at 600 and

1800 kHz.

Annex A


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17Ferroxcube

Fig. B1 Circuit diagram.

Annex B


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18Ferroxcube

Fig. B2 Component placement - top side. Fig. B3 Component placement - bottom side. Fig. B4 PCB layout - top side.

Fig. B5 PCB layout - bottom side. Fig. B6 PCB layout - GND layer

Annex B


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19Ferroxcube

Part reference Part number Description Package Manufacturer

C1, C2, C3, C4 18122R105K9BB0D Ceramic capacitor: 1F, 50V 1210 Phycomp

C5, C6, C7 T510X477K006AS Low ESR tantalum capacitor: 470F,6V

2220 Kemet

C8 12062R106K7BB0D Ceramic capacitor: 10F, 10V 1210 Phycomp

C9 12062R104K9BB0D Ceramic capacitor: 0.1F, 50V 1206 Phycomp

C11, C12 12062R224K9BB0D Ceramic capacitor: 0.22F, 50V 1206 Phycomp

C14 12062R471K9BB0D Ceramic capacitor: 470pF, 50V 1206 Phycomp

C15 12062R105K7BB0D Ceramic capacitor: 1uF, 16V 1206 Phycomp

D1 IRF7807 N channel MOSFET SO8 International Rectifier

D2 IRF7805 N channel MOSFET SO8 International Rectifier

D3 STPS340U 3A Schottky Diode SMB SGS-Thomson

D4 BAT64 120mA Schottky Diode SOT23 Infineon

D5 MBRS130LT3 1A Schottky Diode 403A-03 Motorola

D6 BAV70 Switching Diode SOT23 Infineon

L1 IIC10G-14/4-3F35 2H, 8A IIC10 Ferroxcube

L2 IIC10-14/4-3E6 Common Mode Choke IIC10 Ferroxcube

JP1 Horizontal Short Actuator RS-Components

R1 RC1206JR-0720R 20Ohm, 5%resistor 1206 Phycomp

R2, R3, R9 RC1206JR-071M 1MOhm, 5%resistor 1206 Phycomp

R4 RC1206JR-07100K 100kOhm, 5%resistor 1206 Phycomp

R7 RC1206JR-073R 3Ohm, 5%resistor 1206 Phycomp

R10, R12 RC1206JR-071K 1kOhm, 5%resistor 1206 Phycomp

U1 MAX1710EEG Controller for dc-dc converters 24-QSOP Maxim

SW1 JUMPER LINK (close) RS-Components

SW2 JUMPER LINK (open) RS-Components

SW13 SWITCH 4 DIP-8 RS-Components

Table B1 Component list

Annex B


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20

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14 watt dc-dc converter using iics

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