Gigabit Ethernet – IEEE 802.3zGigabit Ethernet – IEEE 802.3zThe Choice of a New GenerationThe Choice of a New Generation

ECE 4006c

G2- Gigabit Ethernet Intel/Agilent TX

Javier Alvarez, gte006r

Astou Thiongane, gt3083a

Ebrima Kujabi, gte212s

Background CoverageBackground Coverage

General Introduction to the Ethernet The IEEE Ethernet Standards

-802.3z Single Mode V. Multimode Fiber VCSELs V. EELs The Specifics of the Project

-The Intel Ethernet Card- The Maxim Evaluation Board

(MAX3287SW EV KIT)

Evolution of the EthernetEvolution of the Ethernet The Internet Revolution and the need for ever Increasing

Bandwidth The Ethernet Advantage:

- Increase in Efficiency

- Larger Capacity

- Lower cost

- Simpler Networks

From Ethernet to Gigabit EthernetFrom Ethernet to Gigabit Ethernet

Why Fiber?Why Fiber?•The two fibers can transmit the same amount of The two fibers can transmit the same amount of information as the bundle of copper wires.information as the bundle of copper wires.

SMF v. MMFSMF v. MMF SMF

- Core Size 9um- 2km w/o losses- No bouncing off cladding

MMF- Core Size 50-100um- Graded v. Step-Index

Graded Index MMF is what is most common and what will be used in this project b/c of low cost.

VCSEL vs. EELVCSEL vs. EEL

VCSELs have a circular laser beam, which is easier to couple with fiber than the EEL’s elliptical beam.

VCSELs are cheaper for several reasons:– They can be tested on the wafer; thus, bad chips can be discarded

early in the manufacturing process.This increases the yield and decreases the unit price.

– The laser beam being circular and perpendicular to the substrate makes it possible to couple it with fiber without rectifying optical lenses.

Project GoalsProject Goals

Test previous semester’s Intel testbed

Replicate transmitter in the opto-module– By using:

Maxim 3287 Evaluation Board Using Reverse Engineering to

design our own board

Test the board by:– Obtaining an eye diagram

Intel Opto-module Intel Opto-module

Pin Assignments: – Pins 1 and 9 are grounds for

the receiver and transmitter– Pins 2 and 3 are differential

inputs for the receiver– Pin 4 is Signal Detect– Pin 5 and 6 are VCC for the

receiver and transmitter– Pins 7 and 8 are differential

outputs for the transmitter.

Intel Opto-module (Cont’d)Intel Opto-module (Cont’d)

The sub-circuit in the the red box is the actual opto-module, which consists of a TX (top) and RX (bottom).

The circuit in the green circle is a filter for the dc power provided to the transmitter and receiver.

Capacitors C9, C10, C11, and C12 provide dc coupling.

Resistors R1, R2, R3 and R4 provide 50 ohm terminations.

Opto-module (Cont’d)Opto-module (Cont’d)

Our Group’s part of the job is to design a transmitter.

The other groups have to design the laser and the receiver.

The figure on the right is a high level drawing of how all three parts will be put together for testing.

General Use of MAXIM boardGeneral Use of MAXIM board

Replace transmitter of Intel opto-module with Maxim 3287.

MAXIM 3287, is a transmitter used to drive the VCSEL for optical transmission.

Maxim Board SpecsMaxim Board Specs

Basic Features– Optimized operation at 1.25 Gbps.– Supports a current modulation up to 30mA.– Deterministic Jitter of approx. 22 ps.– Requires a 3.3 V to 5V power supply.

Component AnalysisComponent Analysis Differential Input (IN+, IN-)

& Output (OUT+, OUT-)– Eliminates noise in channel

Reference Voltage (REF)– Used for programming a laser

bias current in VCSEL applications (~0.8mA)

– Feature disabled for this project

Monitor Diode (MD)– Monitors Laser Current– Not supported by board

Component Analysis (Cont’d)Component Analysis (Cont’d)

Current Modulation Control (Pin 15)

Temperature Coefficient Control (Pin 16)

AC Coupling AC Coupling • Remove R20 (49.9)

• Replace R24 (24.9) with R20

Safety FeaturesSafety Features

Shutdown Driver Output (SHDNDRV) Power-On Reset (POR)

– Resets Laser when turned off.– Rejects Noise caused by VCC during power-on or hot

plugging. Bias Controlling Transistor Driver (BIASDRV)

– Transistor placed between BIASDRV and VCC– Ensures Low Noise Operation– Rejects Power Supply Noise

Decoupling Capacitors at VCC & GND

Board DesignBoard Design The Figure below shows a PSpice schematic of the

new board design without the safety features.

Board Design (Cont’d)Board Design (Cont’d) Parts List Consists:

Transmission Line IssuesTransmission Line Issues To avoid transmission line problems, wires should

not be longer than 1/10 of a wavelength. Using the equations in the figure below, it was

determined that the wires should not be longer than 4mm.

IEEE 802.3z Eye MaskIEEE 802.3z Eye Mask

The Eye Mask from IEEE 802.3z on the figure shows the distinction between a logical 1 and 0

An open eye represents proper functionality

PCB LayoutPCB Layout In order to avoid

transmission line problems, components in the signal path were placed close to the pins on the Maxim chip.

The trace widths and separations were laid out to match the manufacturer’s (Bob House) specifications.

New Populated boardNew Populated board

The figure to the right shows the board that was designed using SuperPCB

The yellow jumper wires connect VCC to certain components because the initial design did not include them.

Quick fixesQuick fixes

The components in the red circles are SMA connectors– They had to be moved

from the top to the bottom of the circuit:

To avoid more Transmission line problems

Make better contact with the board.

Maxim Board Eye DiagramsMaxim Board Eye Diagrams

• Eye from DC coupled board.

• Overshoot at bottom could be attributed to:

-Power Supply noise

- Inductance from board

• Eye from AC coupled board

• Overshoot at bottom is smaller than when DC coupled.

•Undershoot at top possibly due to using 47 termination, instead of 49.9.

Eye Diagram from New BoardEye Diagram from New Board

The eye diagram was from a simple square wave (D215) produced by the BERT.

An open eye could not be obtained from the other bit patterns.– This could be attributed

to transmission line problems.

TroubleshootingTroubleshooting

The red arrows show where the pins were connected to the traces via small metallic wires.– The length of these

wires might be the major contributor to transmission line problems.

RecommendationsRecommendations

Redesign the board using SuperPCB to incorporate all the fixes.

Be very cautious about transmission line problems.– The lines to be considered the most are the ones

lying on the signal path.