Synchronous Ethernet Customer

7/22/2019 Synchronous Ethernet Customer

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CONFIDENTIAL INFORMATION

US-TCXOs

- RPT7050

- RPT5032OCXOs

- Mercury

- ROX2522

Rakon Solutions forSynchronous Ethernet v6


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What is Synchronous Ethernet?

Ethernet is traditionally asynchronous Each node has an independent clock

Original intent of packet networks was for bursty, variable rate traffic

Large contiguous flows were managed at higher level Input buffers and high level protocols (Pause frames) manage data flow

Friday, 20 September 2013 2

Ethernet

PHY

Ethernet

PHY

~

Data

100ppm

~100ppm


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Synchronous Ethernet

As services over Ethernet changed to constant bit rates

and real-time, synchronization became required Eg. Live Video, Audio services

Eg. Support for Mobile Back haul

Synchronous Ethernet extends TraditionalSynchronization to Ethernet


Ethernet

PHY

Ethernet

PHYData

PLL

~Primary Reference Clock(Network Clock)PLLLine Extracted

ClockSystemClock

SyncE

TCXO

Synchronization Flow

Ethernet

PHY


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Relevant Standards

G.8010 defines functional architecture of Ethernetnetworks

G.803 describes architecture of transport networksbased on SDH

G.8261 describes timing and synchronization aspects inpacket networks

G.8262 defines Synchronous Ethernet Equipment Slave

clocks (EEC) similar to clocks in G.813 and G.812 G.8264 includes the Synchronization Status Message

(SSM) equivalent in Ethernet Networks



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Implementations

PLL implementations are almost always digital

Low loop bandwidths in the analogue domain are difficult Digital offers additional features

Input Clock monitoring

Reference Switching

Disadvantage is that Silicon Jitter is high


Phase

Comparator

& MonitorsRecovered Clocks

Loop

FilterDCO

Oscillator

Output

Synthe

sizers


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Freerun Accuracy

When the system operates by itself, what is output frequency accuracy?

The DCO (Digitally Controlled Oscillator) freerun output will be output accuracy Since DCO is driven by Oscillator and therefore its accuracy will be the oscillators This is different from Holdover, as Holdover is after disciplining the DCO to a value

EEC oscillators to be at 4.6ppm, accuracy including all deviations Stratum 3 and Stratum 3E accuracies are at 4.6ppm

Pluto/+ and RTX family of TCXOs and Mercury OCXOs 90% applications only need TCXOs


Phase

Comparator& Monitors

Recovered Clocks

Loop Filter DCO

Oscillator

Output

Synthesizers

For Output accuracy

to be at 4.6ppm, the

oscillator accuracy to

be at 4.6ppm


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Wander Generation

Ideal input is applied at the input and output variation is measured Under a constant temperature and a temperature ramp

Depending on PLL loop bandwidth Oscillator noise appears at the output Since the input is ideal, contribution of PLL to output variation is nothing, all depends upon

temperature and aging performance of the oscillator

Option 2 loop bandwidth is 0.1Hz, time constant of 1.6s, TCXO may bechallenged for temperature stability Slope performance (ppb/C) is important


Phase

Comparator

& Monitors

Recovered Clocks

Loop Filter DCO

Oscillator

Output

Synthesi

zers

For Output stability (MTIE& TDEV) to be below

mask, Oscillator

temperature performance

to be tested



Wander Generation Continued

The RPT7050/5032A family has excellent temperature &Slope performance

TCXO thermal design considerations are still very important andneed to be carefully applied (Application note available). Forexample the location of the TCXO in respect to Fans and heat

source.

Some applications with extreme temperature variationconditions may call for an OCXO

This depends on the customer application requirement

The Mercury and/or an oscillator from the traditional OCXOfamily (i.e. ROX5022) should be used




Jitter Performance

The PLL could be directly driving the PHY reference clock

Oscillator to PLL output multiplication, Clock multiplication inside the PHY,Electrical to Optical conversion, power supply variations and layout design - alladds to additional jitter and these effects need to be considered

Eg. 10G PHY needs



Holdover Requirements

Holdover System output is held constant when input is lost. Defined by:


Phase

Comparator

& Monitors

Recovered Clocks

Loop Filter DCO

Oscillator

Output

Synthesi

zers

Output TIE is to be

limited by Oscillator

temperature behaviour,

aging and drift

RPT7050/5032 family meet all such requirements, Mercury outperforms by a mile

Initial holdover accuracy +/- 50 PPB Best case system accuracy

Oscillator temperature stability +/- 2 PPM Usualy -40 to +85 deg C

Oscillator Aging +/- 100 PPB/24hrs

Other effects (Vss, load, etc.) +/- 100 PPB/24hrs Only for option 2

Initial phase jump +/- 120 ns Occurs because of entry to holdover



EEC Oscillator requirements summary

Frequency accuracy At +/- 4.6ppm

Wander Generation F v T performance and aging need to be excellent

Most variations will be filtered by PLL, but quick variations will

pass through

Jitter generation Lower the jitter, the better

Holdover F v T performance, aging and drift parameters are critical

RPT7050/5032 family passes with flying colours




G.8262 Solution Vendors

ADI AD954x family devices

IDT

8vxxxx family of devices

Microsemi Corporation

ZL3014x family, ZL3016x family devices

Semtech

ACS95xx family of devices

Silicon Labs

Si9528 family of devices




Summary

Rakon Pluto/+ and RTX family TCXOs and Mercury familyOCXOs are well qualified for Synchronous Ethernetapplications supporting ITU-T G.8262 standards

Rakon has worked with all Timing Silicon vendors to

qualify oscillator solution for Synchronous Ethernet

Rakon has wide range of oscillators to support customersbased on specific requirements


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Documents

Synchronous Ethernet Customer