EMC: Electronics system integration for HEP experiments

EMC: Electronics system yintegration for HEP experiments

(Grounding & Shielding)(Grounding & Shielding)

F ArtecheF. Arteche

OUTLINE• 1. EMC integration strategy • 2. Grounding2. Grounding• 3. Block diagram (EMC map)• 4 EMC unit analysis• 4. EMC unit analysis

– Noise emissions– Noise immunity– Coupling pathp g p

• Cables• PCB• PCB

• 5. Conclusions

1 de 54 Meeting on Power Supplies, Services and GroundingMPI - Munich, 08 March 2010

1. EMC integration strategyTh i l i t th t f f• The main goal is to ensure the correct performance of HEP detectors or experiments.

E th tibilit i h b t– Ensure the compatibility in each sub-system– Ensure the compatibility between units – sub-systems

It t bli h f t i• It establishes a safety margin• EMC integration strategy is carried out in three stages:

G ( )– Grounding issues (strategy)– Block diagram (EMC map)– EMC unit analysis

Compatibility C ibiliCompatibility

SUB1 SUB2

Compatibility Compatibility


SUB1 SUB2

1. EMC integration strategyIt li TOP BOTTON BOTTON TOP h• It applies TOP-BOTTON-BOTTON-TOP approach– Detector-Sub-system-EMC unit

C f– EMC unit identification– Minimum unit that represents each sub- system

• EMC unit analysis is carried out by– Identification & evaluation of noise sources– Identification & evaluation of noise immunity at FEE level– Identification & evaluation of coupling paths

• The identification & evaluation are based on :– Standardized measurements– Non- standardized measurements– Electromagnetic models (simulation)


g ( )

2. Grounding• What is a ground ?• What is a ground ?

– It is a referenceU if f lt t f• Uniform reference voltage at any frequency

– It is a structure to bypass currentsF lt ( h t i it )• Fault (short circuits ..)

• NoiseR f G di• Reasons for Grounding – Safety– Equipment protection– Equipment performance

• Golden rule:– “Make the system safe and then make it work ”


2. GroundingR d ti f d di d i• Recommendation for good grounding designs:– Selection of reference ( grid 3D or plane )

• Detector & Experiment level– Reinforcement structure

A t l t t– Any metal structure• It should have low impedance from DC to High frequency

Safety ground & Equipment protection– Safety ground & Equipment protection• Laboratory codes and European directives.

Metal parts that can be energized should be– Metal parts that can be energized – should be grounded

– Ground connections - Bonding and strapsg p• Ground path should be free of operational currents


2. Grounding• Recommendation for good grounding designs:g g g g

– Ground to improve the equipment performance• Multipoint ground topology is the preferred option

– Multiple ground connection to ground– Digital and analog has to be grounded separate and later

connected to common point at board levelconnected to common point at board level– Electronics , hardware and power parts should be grounded

separately at module level and then connected together • Ground connection has to be short

– It has to present low impedance path at high frequency


2. Grounding• One single connection a few cmOne single connection a few cm

– It resonates 14 MHz• Multiple connections

– It resonates above 50 MHz• Main characteristics of multiple

d tiground connections – They should be connected to:

• Opposite corners of theOpposite corners of the equipment

• The nearest points on the signal reference gridssignal reference grids.

• Very special cases it can be done via capacitorsp– Several


2. Grounding• Recommendation for good grounding designs:• Recommendation for good grounding designs:

– Ground designs to improve the equipment performanceperformance

• At LF – Avoid ground loops – Detector is a kind of resistor divider where currents flows

everywhere• At HF – Avoid noise currents pass through sensitive parts

E thi i t d ( l iti i d ) d– Everything is connected (real or parasitic impedance) and designing a low impedance paths for these currents

– All experiment subsystems has to present the sameAll experiment subsystems has to present the same ground topology.

• They have to be coordinated y– It is recommended to have an schematic ground

design first and later mechanical ground design


2. Grounding Experiment levelExperiment level


System level2. Grounding

PhotocathodMetal

HV Backplane

+Bias Voltage

-High Voltage

Metal fixture

HPDSignal pixel

10 M

1G

1GCourtesy : Dr. Rivetta (SLAC)

g

Interface card

Guard ring

10K200 M

100K

4 CH. FILTER

80 nf

10K

Electrical BackplaneShield Grounding

1M

Equivalent to pixel

capacitance

V-

0

V+

DPMT d

p

Floating

low voltage

Grounding

Plug-in HV Module

Differential current amplifier

QIE

card

QIE

voltage power

supplies12 kV & 200 V power voltages for HPD. Cable

Global & System grounding policy have to be di t d

length ≈ 500 ft


coordinated

3. Block diagram (EMC map)

• The block diagram is used to :– Identify sub-systems– Power levelsPower levels – Noise sources and victims

C li h– Coupling phenomena• It helps to define the EMC unitp

– All studies and analysis will be focused on this unit to ensure the correct electronicsthis unit to ensure the correct electronics integration


3. Block diagram (EMC map)Slow control

Tracker

2 5V 1 25 V

Radiation

Slow control

Transients

2.5V, 1.25 V

500 V

FEE

Conductive Noise Distribution

Bus (AC)SMPS

Noise

FEE (dc)

RadiationN i

SMPSAC-DCHarmonics

Radiation RadiationNoise

FEE (dc)SMPSAC DC

Noise Noise

FEE (dc)SMPS

Conductive Noise

RadiationNoise

AC-DCConductive

NoiseRadiationNoise

• CMS EMC map – Block diagram

NoiseNoise

Slow controlShielding

HCAL

6.5 V, 4.5V


Shielding7 kV

4. EMC unit analysisHEP i t l• HEP experiments are very complex– The idea is to define general rules emerging from particular

sub-systems (TOP-BOTTON-BOTTON-TOP approach)sub systems (TOP BOTTON BOTTON TOP approach)• HEP sub-detectors can be considered as isolated system

– Power Supply & Slow control system only galvanic pp y y y gconnection.

• A reduced model of the sub-system is considered for EMC t d f HEP i tstudy of HEP experiment– Noise sources – PS – Coupling path - Cables

VictimCoupling path Cables

– Victim - FEEDetectorFEEP.S. Voltage Distribution DetectorFEEP.S. DetectorFEEP.S.

Optical Link

DetectorFEEP.S.

Optical LinkNoise sourceCoupling path


Coupling path

4. EMC unit analysis

• HCAL EMC FEE unit – 1 RBX– Two boards connected

• TEC FEE unit – 1 PetalPetal divided in Two boards connected

– PCB – Petal divided in

– Rings & Modules– ICB- Inter Circuit Board


4.1 EMC unit analysis: Noise emissions• Switching converters generates conducted noiseSwitching converters generates conducted noise

– At the input & output– Two modes of noise emissions (from kHz to MHz range)( g )

• Common mode • Differential mode

Power switching converter

Switching devices Filter


Switching devices Filter


Switching devices Filter CM Filter


Switching devices Filter CM Filter

Load

g

Idm Load

g

Idm

Sw tc g dev ces

Icm

Sw tc g dev ces

IcmLoadLoad

GndGndGnd Gnd

Parasitic capacitance of heat sink

Gnd

Parasitic capacitance of heat sink

DM CMDM CMMeeting on Power Supplies, Services and Grounding

MPI - Munich, 08 March 201015 de 35

4.1 EMC unit analysis: Noise emissionsC d (CM)• Common mode (CM)– Group of conductors and ground or other conductors– Origin in DC/DC converters

• Magnetic ( dI/dt high )• Electric field (dV/dt high)• Path - Parasitic capacitive or inductive coupling

Diff ti l d (DM)• Differential mode (DM)– Conductor pairs (Negative-Positive or Phase-Neutral)– Origin direct result of fundamental operation of the

deviceP th N l l t i l i it• Path – Normal electrical circuit

• Abundant energy exchange between modes CM t DM i– CM to DM conversion


4.1 EMC unit analysis: Noise emissions

I+VICOR - HCAL

+CdId

-Cm

Icmmeas

Icm/2 Icm/2

• Output currents –(ref. = 50 ohms)


4.1 EMC unit analysis: Noise emissions1 unit Vs 50 units

•Multiple PS units may increase the noise level•Design issue Filtering


•Design issue - Filtering

• But ..Are the PS noise emission compatible with the FEE ??4.2 EMC unit analysis: Noise immunity

p– Do we have enough safety margin ?

• Noise sources that deteriorates the FEE performance are:I t i i th l i– Intrinsic thermal noise

– EM noise picked-up by the connection detector - FEE– EM noise picked-up by the connection FEE - Power supplyEM noise picked up by the connection FEE Power supply

K+++= (t)n(t)n(t)n(t)n psintha

• This noise defines the minimum signal level that the FEE can process –Thermal noise dominant effect– Design – Minimize Thermal noise– Characterize the EMI contributions and decrease its effects

• The characterization of EMI contributions– Modeling and simulation of systemg y

• Robust designs & coupling mechanism– Immunity tests on prototypes

• Weak points & Noise characterization


p• Compatibility

• The main goal is to define the immunity of the FEE to RF4.2 EMC unit analysis: Immunity- Test

The main goal is to define the immunity of the FEE to RF disturbances– Diagnosis– Detection of sensitive areas – FEE frequency response to noise – Evaluate solutions– Noise emission specification from PS

• Inject a perturbing signal to the FEE and evaluate the FEE performanceF (kH t 50 MH )– Frequency range (kHz up to 50 MHz or more)

– Test layout ( EMC unit) as similar as possible to the final configuration

• Many test configurations may be studiedMany test configurations may be studied– Shield currents – CM and DM currents – Power lines & slow control lines

• Test performed on the FEE: EMC unit

FEEFEEFEE( )ti t ( )tV20 de 35 Meeting on Power Supplies, Services and Grounding

MPI - Munich, 08 March 2010

FEEFEEFEE( )ti pert ( )tVout

4.2 EMC unit analysis: Immunity- Test

25

30Reference8 MHzHCAL

20

nts]

10

15

[RM

S C

oun

5

Pre-shower0 5 10 15 20 25 30

0

Channel number

• Diagnosis & Sensitive areas

Pre-shower

• Diagnosis & Sensitive areas– HCAL – Ground connection photodiodes-Board– Pre-shower - Ground connections between paths


Pre shower Ground connections between paths

4.2 EMC unit analysis: Immunity- TestFreq enc response• Frequency response– It is the noise transfer function (TF) of FEE

T tif th ibilit f th FEE t i t• To quantify the sensibility of the FEE to noise currentsExternal Noise

TFVout (RMS)Icm

)(V)()()(

1

1

ωω

ωcm

out

IVTF =


CMS4.2 EMC unit analysis: Immunity- Test

CMS Trackerse

spon

y re

s APV chip Tracker FEE

ency

eque

CMS

Fre CMS

PreshPACE chipPre-shower

FEE



A B

E l t l ti (HCAL)• Evaluate solutions (HCAL)– Ground connection of the shield – 3 configurations

• Length strap & Routing pathLength strap & Routing path– GND1 - Plot A– GND 2 – Plot B without cooper sheet

GND3 Pl t B24 de 35 Meeting on Power Supplies, Services and Grounding


– GND3 – Plot B

4.2 EMC unit analysis: Immunity- Test100HCAL

10-1

10

CM TF - PK APV 632 - CM FILTER CM TF - PK APV 632

HCAL

10-2

mA]

10-3

F - [

Coun

ts / m

10-4

TF105 106 107

10-5

Frequency [Hz] Trackerq y[ ]

• Evaluate solutions– CM filter performance


p


• Noise emission specification – HCAL – 3 Topologies (GND, FILTER,NO EXTRA)– Very different from standards


– Very different from standards

4.3 EMC unit analysis: Coupling path• PS units & FEE are connected through power networks

– Long cablesC– Long PCBs

• It´s very important to study the effect of these power networks in the noise propagation and radiationnetworks in the noise propagation and radiation. – It helps to define the EMC environment

It helps to established the safety margin among noise– It helps to established the safety margin among noise emissions & susceptibilities

– It helps to improve the susceptibility of the FEE (only a very p p p y ( y yearly stage of the design)

• The analysis can be carried out using:– Numerical simulation programs– Real measurements


4.3 EMC unit analysis: Coupling path - Cables

• Noise propagation effects of long cables in HEP power system

The specific config ration of FEE (inp t capacitors)– The specific configuration of FEE (input capacitors)• Attenuates CM & DM voltages • Amplifies CM & DM currents )(

)()(fIfIfGain out=• Amplifies CM & DM currents

– Cable radiation )0(&)0( IIVV )0(&)0( IIVV

)( fI in

ICM

EMI FilterCable

)0(,&)0(, cmdmcmdm IIVV)(,&)(, LIILVV cmdmcmdmICM

EMI FilterCable

)0(,&)0(, cmdmcmdm IIVV)(,&)(, LIILVV cmdmcmdm

FEE

IDM VDM

FEE

IDM VDM

FEEICM

PS UnitGndV

FEEICM

PS UnitGndV


4.3 EMC unit analysis: Coupling path - Cables• Radiation emission from cables may be studied with a• Radiation emission from cables may be studied with a

simple test– Several configurations may be analyzedg y y

Near field probe(H)TSP cable (H)

BCI probeCurrent probe

PS circuitLoad circuit

Meeting on Power Supplies, Services and GroundingMPI - Munich, 08 March 2010

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4.3 EMC unit analysis: Coupling path - Cables

30 dB

20 dB

• The best solution to reduce the effects on the FEE and vicinity of currents flowing through the cable :vicinity of currents flowing through the cable :– Connect the shields at BOTH ENDS (at HF)

• Reduce the ability of cables to radiates• One side via capacitor to avoid ground loops at LF


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HF t fl th h th hi ld d bl t

4.3 EMC unit analysis: Coupling path – Cables• HF currents flows through the shield and cable tray

– Generated by Near and Far fields as well as HF ground currents– It couples an small amount of energy in the inner conductors

• This coupling mechanism is characterized in cables by the surface transfer impedance– Its impact is easy to evaluatep y

• In case the shield is not present or it is connected only at one end, noise currents are induced directly in the central conductors by external magnetic fieldconductors by external magnetic field

• Because the low impedance of the circuit associated with those cables


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4.3 EMC unit analysis: Coupling path - PCB• Also PCB may radiate and decrease the performance of the FEE• Also PCB may radiate and decrease the performance of the FEE• As an example – CMS Tracker system

– The main noise source of CMS tracker system is the radiated emissionThe main noise source of CMS tracker system is the radiated emission of Power Network (ICB)

– Radiated noise generated mainly by CM currents injected by Power S liSupplies

• Noise currents on power network– Magnetic field – Not uniform

A

B

C

D E


4.3 EMC unit analysis: Coupling path PCB60 65

50

55

60

55

60

65

BBy

35

40

45

40

45

50

dBµV

Bx

25

30

35

Hx (at 10 MHz)( )

30

35

40

90

100

110

20Hx (at 1MHz)

A B C D E25

A B C D E

50

60

70

80

90

EE – field

UniformH – field

Not uniform

10

20

30

40E (at 10 MHz)E (at 1 MHz)

Uniform

Mod/ RodNot uniform

Mod / Rod0

A B C D E


• EMC integration strategy for HEP experiments has been5 CONCLUSIONS

• EMC integration strategy for HEP experiments has been presented– They have analyzed the noise sources, coupling path and victimy y p g p– They have presented some design criteria,

• Grounding policy & EMC requirements & EMC test• EMC studies should start at design level

– It should involves all disciplines – Mechanical , electrical……All di i li h t b di t d UNIQUE ENTITY• All disciplines has to be coordinated – UNIQUE ENTITY

– It saves money, time and “discussions between groups”.– CMS upgrade has seriously considered these issuesCMS upgrade has seriously considered these issues

• 9.04 : EMC studies for CMS tracker upgrade - Approved• EMC requires a systematic analysis to obtain good results

– It very important to start with simple models (T-B-B-T approach)– Extend conclusions for the final system

EMC di i i &35 de 35 Meeting on Power Supplies, Services and Grounding


• EMC studies requires time & manpower.

EMC: Electronics system integration for HEP experiments

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