POF Knowledge Development EMC Lessons Learnt on Gigabit Ethernet - - PowerPoint PPT Presentation

AESIN CONFERENCE | 2nd Oct 2018

POF

Knowledge Development

Rubén Pérez-Aranda (rubenpda@kdpof.com)

EMC Lessons Learnt on Gigabit Ethernet Implementation for ADAS & AV

AESIN CONFERENCE | 2nd Oct 2018

POF

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

2

AESIN CONFERENCE | 2nd Oct 2018

POF

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

3

AESIN CONFERENCE | 2nd Oct 2018

POF

The target: GEPOF Ethernet PHY

4

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, …

AESIN CONFERENCE | 2nd Oct 2018

POF

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

5

PHY

Power management PS filters and protections

Wake-up & Sleep

Indicators Management I/F Configuration Battery SFP I/F (SGMII, 1000Base-X)

SyncE

AESIN CONFERENCE | 2nd Oct 2018

POF

Noise emissions compliance (EMI)

6

• RE. In front of the EUT
• RE. In front of the harness

1 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 method

0.15 MHz < f < 30 MHz 0.15 MHz < f < 320 MHz 0.15 < f < 108 MHz Monopole antenna Current clamp LISN (AN)

AESIN CONFERENCE | 2nd Oct 2018

POF

Noise immunity compliance (EMS)

7

RI, RF. In front of the EUT RI, RF. In front the harness RI, BCI 1 GHz < f < 6 GHz. CW, PM217 200 MHz < f < 1 GHz. CW, AM, PM18 0.1 MHz < f < 400 MHz. CW, AM Horn 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 transmitters 1.2 — 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

AESIN CONFERENCE | 2nd Oct 2018

POF

Lesson 1: standards vs. OEM’s specs

8

• 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

AESIN CONFERENCE | 2nd Oct 2018

POF

Lesson 2: the EMC qualification process

9

Redesign EMC Pre- compliance EMC Compliance

N cycles M cycles

M <<< N

EMC Qualified

1× EMC compliance session 1× EMC pre-compliance laboratory

=

COST

AESIN CONFERENCE | 2nd Oct 2018

POF

EMC pre-compliance: radiated emissions

10

TEM cell EUT

POF PORT

Port 1 Port 2 DC-block 50Ω load

RF shielding box

LNA 40dB

SA

LISN LISN

PSU 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!

AESIN CONFERENCE | 2nd Oct 2018

POF

EMC pre-compliance: conducted emissions

11

TEM cell EUT POF PORT

RF shielding box

SA

LISN LISN

PSU 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

AESIN CONFERENCE | 2nd Oct 2018

POF

EMC pre-compliance: radiated immunity

12

RF-HPAs RF-HPA PSU SA monitor Pulses 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

AESIN CONFERENCE | 2nd Oct 2018

POF

Lesson 3: Power supply (CM & DM) filters

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

AESIN CONFERENCE | 2nd Oct 2018

POF

Lesson 4: PM IC spread-spectrum

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

PM IC simulation predicts noise reduction

AESIN CONFERENCE | 2nd Oct 2018

POF

Lesson 5: DSP and RGMII spread-spectrum

15 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

AESIN CONFERENCE | 2nd Oct 2018

POF

Lesson 6: SGMII interface

16 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

AESIN CONFERENCE | 2nd Oct 2018

POF

• 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

17 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

AESIN CONFERENCE | 2nd Oct 2018

POF

Lesson 8: 25 MHz XTAL vs. Oscillator

18 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

AESIN CONFERENCE | 2nd Oct 2018

POF

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

19

• 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

AESIN CONFERENCE | 2nd Oct 2018

POF

Lesson 10: XTAL layout for immunity performance

20

AESIN CONFERENCE | 2nd Oct 2018

POF

Knowledge Development

Thank you!