Gigabit Ethernet – IEEE 802.3z The Choice of a New Generation ECE 4006c G2- Gigabit Ethernet...
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Transcript of Gigabit Ethernet – IEEE 802.3z The Choice of a New Generation ECE 4006c G2- Gigabit Ethernet...
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.