AltiumLive 2017:

Component selection

for EMC

Martin O’HaraVictory Lighting Ltd

Munich,24-25 October 2017

▪Passives▪ resistors, capacitors and inductors

▪Discrete▪ diodes, bipolar transistors, FETs

▪Integrated Circuits▪ logic, microprocessors, i/o interface

▪Others▪ crystals, heatsinks

Component Selection

▪Surface Mount Preference▪ lower parasitic inductance and capacitance

▪Smaller Parts Usually Better▪ same reason as above

▪Be Aware of Mechanical Effects

▪Avoid Sockets in Production▪ add more parasitics

Component Packaging

▪Surface Mount Preference▪ lower parasitic inductance and capacitance

▪Carbon and Film Preferred▪ have more high frequency losses than metal

▪ no intrinsic resonances of significance

▪Wirewound Highly Inductive▪ can be reduced by winding style

▪ Noise Voltage Not Critical to EMC

Resistors

Chip Resistors

100R, 0805

1GHz100kHz

Impedance

(Ω

)

10

10,000

100

1000

▪Surface Mount Preference▪ parasitic inductance limits frequency response

▪Low Equivalent Series Resistance▪ higher rejection at specific frequencies

▪Low Equivalent Series Inductance▪ limits frequency response

▪Cure many EMC problems at circuit level▪ filtering, decoupling, slew limiting

Capacitors

▪ 4-Element Model Simulates Impedance Characteristics

▪ Rs - series resistance

(resistance of lead/electrodes)

▪ ESL – equivalent series inductance (inductance of lead/electrodes)

▪ Rp - dissipative resistance (leakage/hysteresis losses)

▪ Cp - primary capacitance

(design value)

Capacitor Model

DC 10Hz 100Hz 1kHz 10kHz 100kHz 1MHz 10MHz 100MHz 1GHz

Mica, Glass, Low-Loss Ceramic

Polystyrene

Ceramic (High-K)

Aluminium Electrolytic

Tantalum Electrolytic

Paper

Mylar

Capacitor Dielectric

Ceramic Dielectrics

Dielectric Self Resonant Frequency (MHz)

Y5V 46

X7R 44

COG 40

Capacitor Lead Length

0.1

1

Imp

edan

ce (O

hm

s)

Frequency

15mm

10mm

0mm

10kHz 10MHz1MHz100kHz

10uF Ceramic Disc Capacitor

ESR Limited Capacitor

1

10

100

Imp

edan

ce (O

hm

s)

frequency

ESR

1kHz 10kHz 100kHz 1MHz 10MHz

0.1

1

10

100

1000

10000

100000

1000000

Imp

edan

ce (O

hm

s)

frequency

2.2nF

100nF

1uF

10uF

Impedance MLCC Capacitors

10Hz 100Hz 10kHz 1MHz 10MHz1kHz 100kHz

0

10

20

30

40

50

60

70

80

90

100

0 5 10 15 20 25 30

Applied DC Bias (Volts)

Cap

acita

nce

as a

Per

cent

age

of N

omin

al (%

) COG

X7R

Y5V

DC Bias of MLCC Capacitors

-70

-60

-50

-40

-30

-20

-10

0

10

-40 -20 0 20 40 60 80 100 120 140

Temperature (C)

Cha

nge

in N

omin

al C

apac

itanc

e (%

)

Y5V

X7R

C0G

Temperature Bias of MLCC

Parallel Capacitors

Parallel Resonance of 1uF and 1nF Capacitors

0.01

0.1

1

10

100

1000

10000

10Hz 100Hz 1kHz 10kHz 100kHz 1MHz 10MHz 100MHz 1GHz

frequency

Imp

ed

ance

(Oh

ms)

▪Surface Mount Not Important!

▪Parasitic Capacitance ▪ effected by winding style (unquoted)

▪ form factor (closed loop or air cored)

▪Few Useful for Higher Frequency Filtering

▪Self Resonance Potential EMC Problem▪ often within radiated emissions band

Inductors

▪4-Element Model Simulates Impedance Characteristics

▪ Rs - series resistance

(resistance of wire)

▪ Cw - winding capacitance

(varies with winding style)

▪ Rp - dissipative resistance

(limits resonance peak)

▪ Lp - primary inductance

(design value)

Inductor Model

0.01

0.1

1

10

100

1000

10000

100000

1000000

10 100 1,000 10,000 100,000 1,000,000 10,000,000 100,000,000 1,000,000,000

Impe

danc

e (O

hms)

frequency (Hz)

10mH

1mH

100uH

10uHW

oLC

f2

1

Inductor Impedance Curves

0.1

1

10

100

1000

10000

100000

10 100 1,000 10,000 100,000 1,000,000 10,000,000

Impe

nanc

e (O

hms)

Frequency (Hz)

Bobbin

Toroid

Rod

Ideal

Lf

RQ

o

p

2

δ

Inductor Form Factor

50

60

70

80

90

100

0 1 2 3 4 5 6 7 8 9

Per

cent

age

of N

omin

al I

nduc

tanc

e (%

)

DC Bias Current (A)

BobbinToroid

Rod

Current Limited Inductance

0

5

10

15

20

1 10 100 1000 frequency (MHz)

Ferrite BeadA

tte

nu

atio

n(d

B)

Ferrite Beads: 1T Inductors

▪Surface Mount Preference▪ lower parasitic inductance and capacitance

▪Diodes▪ unusually fast is often good for EMC

▪Transistors▪ opposite of above!

Discrete Components

Discrete Component Packaging

Package Type Lead and BondWire Inductance

(nH)

Inter-LeadCapacitance

(pF)E-Line 5 0.15

SOT-23 2.5 0.08

▪Terminate Base/Gate Drive from Logic▪ high R for BJT, low R for FET

▪Bipolar Higher ESD Tolerance▪ back-to-back diode structure beneficial

▪Slew Limit Drive with Capacitor▪ BJT can switch very quickly

▪ BJT/FET can demodulate RF as EXP/SQ law

Transistors: Generalisations

Soft recovery best for

lower ripple

Reverse Recovery Time

▪Surface Mount Preference▪ lower parasitic inductance and capacitance

▪Digital Components▪ use lowest speed you can functionally

▪Analogue Components▪ look for bandwidth limited parts

▪ slew rate limiting now popular (for good reason)

▪Avoid Using Sockets in Production

Integrated Circuits

Dual-in-Line (DIL)

Small Outline (SOIC)

Plastic Leaded Chip Carrier

(PLCC)

Lead Count

L (nH) C (pF) L (nH) C (pF) L (nH) C (pF)

8 6.3 0.68 3.1 0.35

14 6.7 0.74 3.2 0.36

16 6.9 0.77 3.4 0.38

20 8.6 1.01 6.7 0.65 4.6 0.62

24 9.1 1.06 7.2 1.14

28 9.6 1.14 5.8 0.72

40/44 11.0 1.25 5.9 0.77

64/68 17.6 1.51 6.1 0.80

IC Packages

www.aseglobal.com

R (mOhms) C (pF) L (nH) Cm (pF) Lm (nH)

MQFP 1.6 16

PQFP 1.7 13

TSOP 90 0.8 5.5

BGA 70 0.5 2.3

uBGA 50 0.25 1.8 0.04 0.2

CWLP 20 0.00531 0.1 0.035

Compliant Wafer Level Packaging

Lead inductance inc at 0.8nH/mm

Lead capacitance inc at 0.1-0.15pF/mm

Bond wire inductance inc. at 1nH/mm

Newer Packages

Ultra-Low Parasitics

Pitch 0.65 0.4 mm

Lm 0.6 1.5 nH

Cm 0.05 1.42 pF

▪ Fine Pitch Packages

▪ increases mutual inductance/capacitance (increases cross talk)

▪ reduced parasitic pin inductance/capacitance (due to shorter leads)

Pin Pitch

Special Package Configuration

Logic Family

Rise/Fall Time (ns)

Bandwidth (MHz)

Noise Margin (V)

Decoupling Capacitor

(nF)

CMOS 100 6.3 1.0 0.47

LTTTL 20/10 20 0.4 0.33

TTL 10 32 0.4 2.20

HC CMOS 10 32 1.0 0.33

LS 10/6 40 0.3 3.30

ALS 4 100 0.4 2.20

S 3/2.5 120 0.3 1.50

F 1.75 180 0.3 1.50

ECL-10K 2 160 0.125 0.22

ECL-100K 1 320 0.125 0.22

Logic Family Parameters

0.0

0.5

1.0

1.5

2.0

2.5

1 10 100

Clock Frequency (MHz)

Pow

er D

isip

atio

n (W

)

100pF

50pF

10pF

0pF

Loaded CMOS Drivers

High Data Rate Drive

1 10 100 1000

Pow

er D

issi

patio

n pe

r Por

t (P

d)

Frequency (MHz)

60MHz-70MHzPECL

CMOS

▪Decouple Every IC▪ can share for low speed, slew limited circuits

▪Calculate C If Possible▪ can use “Rule of Thumb”

▪Multiple Decoupling for Microprocessors▪ every supply pin

▪ parallel capacitors of 1:100

▪Lower Cost than Large Bypass Capacitor

Decoupling Capacitors

Spread Spectrum Clocks

-4 -3 -2 -1 0 1 2 3 4

Am

plit

ud

e (d

Bu

V)

Modulation (%)

Spread Spectrum Clock

Standard Clock

▪Trend for Low Operating Voltage

▪Reduces Current Surges

▪ hence decoupling requirement reduced

▪Reduced Emissions

▪ for same rise/time and frequency 3.3V has 3.6dB lower emissions than 5V part

▪Increased Susceptibility

▪ Avoid or buffer at interfaces

▪ differential signalling improves susceptibility

Low Operating Voltage

▪IC Manufacturer May Change Process▪ improve their yield, increases rise/fall time

▪ won’t advise if no parametric change

▪Not All IC’s Made The Same▪ different manufacturers, different EMI performance

▪ EMC is not a usual datasheet parameter

▪Emission Problem with Digital ICs▪ datasheets specify maximum time parameters only

▪Susceptibility Usually with Analogue ICs

Buyer Beware

▪Transformers▪ similar to inductors for EMC parameters

▪Thyristors, TRIACs, SCR’s etc

▪DC-DC Converters and SMPS▪ often bought as component

▪Electromechanical▪ relays, switches, heatsinks, cabling

▪ use snubber circuits on relays and switches

Other Components

tw

tp

tr

Ideal Square Wave

r

w

p

o

tf

tf

tf

1

1

1

2

1

fo f1 f2

Frequency Domain

Switched Mode Power Supply

0

10

20

30

40

50

60

70

80

90

100

100000 1000000 10000000 100000000

Frequency (Hz)

Co

nd

uct

ed

Em

issi

on

(d

Bu

V)

20dB/decade

40dB/decade

▪Component Selection for EMC is Secondary to Functional Selection

▪Preference for SMD over PTH

▪Generally Slower is Better▪ “fit for purpose”, no need for 100MHz controller on a washing machine

▪ except diodes

▪Use Where Other Criteria are Exhausted▪ note: slower is usually lower cost!

Summary

Thanks for your Attention!

Questions?