emc lessons learnt on gigabit ethernet implementation for ...€¦ · why emc topic? • adas &...

AESIN CONFERENCE | 2nd Oct 2018

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Knowledge Development

Rubén Pérez-Aranda([email protected])

EMC Lessons Learnt on Gigabit Ethernet Implementation for ADAS & AV

mailto:[email protected]


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KDPOF in a nutshell• Fabless silicon vendor

• KDPOF develops state of the art semiconductors for optical communications of 100 Mbps, 1 Gbps, and nGbps for Automotive applications, among others

• Incorporated in 2010. ~30 workers, most of them Engineers

• Located in Tres Cantos, Madrid, Spain

• ISO 9001:2015

• Standardized technology: IEEE Std 802.3bv “Physical Layer Specifications and Management Parameters for 1000 Mb/s Operation Over Plastic Optical Fiber”

• KDPOF supplies Ethernet PHY chipset for many automotive applications: HV batteries, BMS, EV, safe backbone, smart antenna modules, infotainment, ADAS, AV

• The key: POF cable harness provides galvanic isolation and is free of EMC problems

• Currently, Tier-1s and OEMs are implementing ECUs with KDPOF chipset for 1 Gbps and 100 Mbps

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Why EMC topic?• ADAS & AV are emerging, demanding to communications networks:• Higher speeds (e.g. ≥ 1 Gbps)• Lower latencies (e.g. < 100 us)

• Ethernet is being positioned to be the communications technology to make the fusion of sensors, actuators and AI computing units

• Faster speeds make more difficult to meet the EMC constraints: • Wider electromagnetic spectrum needs to be used• Systems become less immune to radiated and conducted noise• Systems emit noise in higher frequencies with higher power

• OK … but POF is optical, … why EMC?

• EMC specifications highly impact in:• The Ethernet PHY IC design: clock strategy, data interfaces, etc.• The integration of the IC at ECU level: schematic, PDN, SI, layout, etc.• The components selection: clock reference, power management, filters, decoupling, etc.

• We will see the process to make a Gigabit Ethernet PHY EMC compliant and the lessons learnt

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The target: GEPOF Ethernet PHY

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1000BASE-RHC PHY compliant with IEEE Std 802.3bv

Optical header connector:‣ PMD sublayer + MDI ‣ TX: driver IC (KD9101) + LED IC ‣ RX: TIA IC (KD9201) + Photodiode IC ‣ Optical lenses for light coupling ‣ Mechanical attachment, mating ‣ EMC shielding (PMD RX handles μA)

Transceiver IC (KD1053):‣ PCS and PMA sublayers ‣ Modulation, FEC, channel equalization,

timing recovery, Ethernet frames en/decoding ‣ MAC layer I/F: RGMII, SGMII, etc ‣ Mixed-Signal IC: DAC, ADC, PLLs, DSP ‣ Safety sensors: voltage, temperature, … ‣ Management: MDIO ‣ PTP, SyncE, …


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Objectives:‣ To be a guide for Tier 1 of how to integrate the PHY in an ECU ‣ To solve components selection (clocks, PMIC, Cs, Rs, Ls, filters) ‣ To solve power distribution networks (decoupling, filtering, stability) ‣ To solve signal integrity ‣ To recommend PCB stack-up and layout ‣ To demonstrate full functionality (e.g. WU/Sleep) ‣ To be a technology evaluation vehicle ‣ To operate in temperature range: -40º — +105 ºC ‣ To support car battery supply conditions ‣ To be EMC compliant w/o metal box

The reference design

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PHYPower

management

PS filters and protections

Wake-up & Sleep

Indicators

Management I/F

Configuration

Battery

SFP I/F (SGMII, 1000Base-X)

SyncE


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Noise emissions compliance (EMI)

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RE. In front of the EUT RE. In front of the harness1 GHz < f < 6 GHz 200 MHz < f < 1000 MHz 30 MHz < f < 200 MHz

Horn antenna. V/H. 3 positions. Logo-periodic antenna. V/H. Biconic antenna. V/H.

RE. In front of the harness CE. Current method CE. Voltage method0.15 MHz < f < 30 MHz 0.15 MHz < f < 320 MHz 0.15 < f < 108 MHz

Monopole antenna Current clamp LISN (AN)


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Noise immunity compliance (EMS)

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RI, RF. In front of the EUT RI, RF. In front the harness RI, BCI1 GHz < f < 6 GHz. CW, PM217 200 MHz < f < 1 GHz. CW, AM, PM18 0.1 MHz < f < 400 MHz. CW, AMHorn antenna. V/H. 3 positions. Logo-periodic antenna. V/H. Current clamp. Several positions, wires configurations.

RI, Radar pulse. In front the EUT RI, Handy transmitters1.2 — 1.4 GHz. 2.7 — 3.1 GHz. PM300 26 MHz < f < 6000 MHz, CW, AM, PM18, PM217, PM300

Horn antenna. V/H. 3 positions. Different antennas


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Lesson 1: standards vs. OEM’s specs

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• Just an example, CISPR 25:2016, radiated emissions between 1 and 3 GHz, component level

• CISPR 25 specifies test and calibration methods, but only give recommendations on the limits

• OEMs norms are usually derived from international standards, with amendments

• If we combine w/c limit of several OEMs (Volvo, JLR, MBN, BMW, Ford), we have a much harder spec to meet


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Lesson 2: the EMC qualification process

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Redesign

EMC Pre-compliance

EMC Compliance

N cyclesM cycles

M <<< N

EMC Qualified

1× EMC compliance session

1× EMC pre-compliance laboratory =COST


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EMC pre-compliance: radiated emissions

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TEM cell

EUTPOF PORT

Port 1 Port 2DC-block 50Ω load

RF shielding box

LNA 40dBSA

LISN

LISNPSU w/ FLT

VBAT

GND

• pre-RE:• Near-field E/H aligned with TEM cell• Far-field results can be correlated if

radiative structures do not change (differential analysis)

• Very useful to debug PDN, SS, decoupling, layout, and noise emissions root causes

• High repeatability!


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EMC pre-compliance: conducted emissions

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TEM cell

EUTPOF PORT

RF shielding box

SA

LISN

LISNPSU w/ FLT

VBAT

GND

RF Splitter

• pre-CE CM:• 0º resistive splitter• It correlates with far-field RE below 1 GHz in front of the harness• It correlates with current method CE < 320 MHz

• pre-CE DM: • Inductive 180º splitter• Used together with pre-CE CM to correlate voltage method and

current method CE results


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EMC pre-compliance: radiated immunity

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RF-HPAs

RF-HPA PSU

SA monitorPulses Generator

RF Generator

PSU (golden, DUT)

RF-Switch (for PM)

RF Shield with TEM CELL

inside

MDIO link margin monitor for sensitivity

Golden

Opt. Att.

PSU DM/CM filters

Eth. tester connection


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Lesson 3: Power supply (CM & DM) filters

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pre-CE CM: RGMII baseline pre-CE CM: RGMII, PS filter


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Lesson 4: PM IC spread-spectrum

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pre-CE CM: RGMII baseline pre-CE CM: RGMII, PS filter, PM IC SS

PM IC simulation predicts noise reduction


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Lesson 5: DSP and RGMII spread-spectrum

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pre-CE CM: RGMII baseline pre-CE CM: RGMII, PS filter, PM IC SS, DSP SS, I/F SS

• KD1053 IC clock architecture was designed from the beginning taking into consideration EMC performance

• 5 PLLs within the IC:• Clean low jitter clocks: 1× PLL for DAC + 1× PLL for ADC• Spread-spectrum modulated clocks: 1× PLL for DSP TX, 1× PLL for DSP RX, 1× PLL for xMII I/F TX

31dB @ 125 MHz

17 dB @ 500 MHz


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Lesson 6: SGMII interface

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pre-CE CM: RGMII baseline pre-CE CM: SGMII, PS filter, PM IC SS, DSP SS, I/F SS

• Data I/F based on SerDes may present additional advantages in EMC:• Differential matched transmission lines vs. single-ended unmatched signals of RGMII• Embedded clock vs. source synchronous transmission with 125 MHz clock of RGMII • Reduced number of traces: 2× TX + 2× RX traces vs. 6 + 6 of RGMII


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• pre-RE TEM cell measurements show noise cleaning produced by clock SS in DSP and RGMII interface

• As higher the harmonic is, the effect of SS is more important

• Highlighted the reduction by SS for some RGMII harmonics

Lesson 7: Spread spectrum is very important in high frequency

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pre-RE: RGMII baseline pre-RE: RGMII, PM IC SS, DSP SS, I/F SS

-14dB

-18dB

-13dB

-16dB

-15dB-16dB

Sinc response due to RGMII random data


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Lesson 8: 25 MHz XTAL vs. Oscillator

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pre-RE: RGMII, PM IC SS, DSP SS, I/F SS — OSC pre-RE: RGMII, PM IC SS, DSP SS, I/F SS — XTAL

• 25 MHz clock reference. Should we use XTAL or OSC? — No easy response from EMC viewpoint• XTAL: better noise emissions performance, cheaper, but it may be worse in immunity• OSC: more robust against noise, but you can measure energy in harmonic +100, because very short tr/tf

• … and MEMS based OSC? — Controlled tr/tf, lower emissions with good immunity. But … worse jitter, which penalizes the sensitivity


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Lesson 9: Differential strip-lines vs. micro-strips

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• After reducing the others, noise peaks from optical transmitter interface become the most important noise

• Current steering differential interface implemented with micro-strip traces • Common mode conversion in the GND (unavoidable, reduced with low inductance GND)• Near E-field coupled into the header connector shield (bouncing) that may act as radiating structure in far-field

• Proposed improvement: strip-lines. To be measured soon … pre-RE: SGMII, PM IC SS, DSP SS, I/F SS

↑E

Near field probe

Micro-strips

Strip-lines


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Lesson 10: XTAL layout for immunity performance

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AESIN CONFERENCE | 2nd Oct 2018PO

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emc lessons learnt on gigabit ethernet implementation for ...€¦ · why emc topic? • adas &...

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