ESDEMC CDE IEEE Symposium 2014

Wei Huang, Jerry TichenorDavid Pommerenke, Viswa Pil la, Pratik Maheshwari , Giorgi Maghlakelidze

Web: www.esdemc.com Email: [email protected] Tel: (+1) 573-202-6411 Fax: (+1) 877-641-9358

Address: 4000 Enterprise Drive, Suite 103, Rolla, MO, 65401

An Ethernet Cable Discharge Event (CDE) Test and Measurement System

http://www.esdemc.com/

mailto:[email protected]

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What is CDE Event ?A Cable Discharge Event (CDE) is an electrostatic discharge between a cable and a connector, it is very common in our life.

Why understanding CDE event is important ?

The discharge processes are complicated due to the number of pins involved and their connections to a system. Both occurrence rate and severity of the static discharge is important to design a robust system.

Desktop, back bone network system

Cable Discharge Event (CDE) Background

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An CDE simulator (Model ES631) is designed to be a commercial test setup to simulate and analyze the ESD events from charged Ethernet cables.

System Features: A well repeatable test setup reproduce CDE events Work with different types of Ethernet cables arrangement (UTP/STP/FTP) Separate status control of each wire for research/ debug

(HV charging / floating / grounding/through) Full control of wire discharge sequence Automatic remove DUT residue charge safely after each CDE test. Integrate probes to monitor discharge waveform on each wire Touch screen UI with USB firmware upgrades for long term functionality Remote control for ATE system integration (LabVIEW, MATLAB)

CDE Simulator Concept

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The CDE system will be consist of several modules and mounted into a Rackmount Cabinet (currently use 12~16 U 19" Cabinet )

1. Main CDE Test ControllerThe main tester will be improved from current CDE design, it should be able to full discharge sequences manually stand-alone and can be remotely controlled via LABVIEW to do arbitrary discharge sequence

2. Charge LAN Cable ModulesThis module simulate typical charged LAN cable setups:

A. line on the air B. line near the groundC. spool of wireD. 8 coax cablesetc…

(We currently have 200 meter close to ground UTP charge module and 200 STP charge module, representing worst cases CDE)

3. LAN Traffic Through Module* (depends on customer needs)This module will connect to the far end of the charged LAN cable and work as a multichannel HV RF switch. After CDE discharge test, CDE main controller can discharge all cables and activate LAN through on both ends of the charge line so operator can test the LAN traffic performance of the DUT.

CDE Simulator Concept – Cont.

Most Common

Second Common

Charge Module A 200 meter long CAT5E UTP Cable with grounded aluminum foil cover cable full length and arranged in 3U Chassis

Charge Module B 100 meter long CAT5E S/UTP Cable with aluminum shielding of the cable grounded and arranged in 2U Chassis

CDE Simulator Cable Charge ModuleES6

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CDE Main Controller Simplified Circuit (HW version 140604)ES6

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CDE Main Controller Test FlowES6

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Pre-Discharge(Triggered by push button or remote)

Discharge(Automatically)

Single wire Discharge

Mode

Differential Pair

Discharge Mode

Contact Sequence Discharge

Mode

Post-Discharge(Automatically)

Wire charging relays are opened if they were

previously closed, DUT discharge relay is opened

too (20 ms)

The discharge relay of the SELECTED WIRE is keep

closed for 1 sec then open

Open the wire discharge relay (15 ms), connect DUT discharge relay and close

the HV charging relays that were previously closed

(200 ms)

Wire Status Control(Idle Status)

Control HV polarity, amplitude and status of

each wire between HV/FL/GND/THR

Same as above

The discharge relays of SELECTED PAIR are closed with 4ms delay between

each relay, then keep relays closed for 1 sec

Open both wire relays (15 ms), connect DUT

discharge relay and close the HV charging relay

(200 ms)

Control HV polarity, amplitude.

All wires are forced to HV connection, no separate

wire status control allowed

Same as above

The discharge relays of SELECTED SEQUENCE are

closed with 4ms delay between each relay, then keep relays closed for 1

sec

Open all wire relays (15 ms), connect DUT

discharge relay and close the HV charging relay

(200 ms)

Same as above


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Wire Status Control

Control HV polarity, amplitude

In single wire discharge mode, additional control of status on each

wire between HV Charging / Floating / Grounding

Through (set voltage to 0, float /ground the wire, then close discharge relays) is available


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Pre-Discharge

Wire charging relays are opened if they were previously closed

DUT discharge relay is opened (20 ms)


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Discharge

The discharge relay of the SELECTED WIRE/ PAIR/ SEQUENCE with 4ms

delay between each relay, then keep relays closed for 1 sec


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Post-Discharge

1. Open the discharge relays(15 ms)

2. Close DUT discharge relay and close HV charging relays that were

previously closed (200 ms)

Typical CDE Test Setup

The typical CDE test setup includes

1. Main CDE tester to manage timing of all charging and discharge event. 2. Different charge modules for different cases3. Oscilloscope to get current (or voltage) signal4. A solid ground reference for CDE setup5. GND and LAN cables6. Shielded coax cable with attenuators for waveform measurement7. Device Under Test

DUT

Oscilloscope

GND wires

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CDE Calibration kit Prototype

In this test, all Cal-kit, short, open, load kit is made for CDE waveform calibration.

All of each part is made of 10 cm long CAT5E UTP cable. The SHORT : each twisted pair is shorted at the end.The OPEN: each twisted pair is opened at the end.The LOAS: each twisted pair is terminated with two 50 Ohm resistors.

During calibration, 5 K/50 Ohm voltage probes are added on each line to monitor the voltage signal, the schematic will be shown for each cases.

Open

Short

Load

CDE Calibration Test Setup

EIA 568B Wiring Cable is used:CH1 = voltage probe on pin 5CH2 = current probe on pin 5CH3 = voltage probe on pin 4CH4 = current probe on pin 4

Voltage probe is 1010:1 (5K/50 resistor bridge = 101:1, plus 20 dB ATT)Current probe is 20:1 (5V/A plus 40 dB ATT)

CDE Controller in all tests is set to 500V, charge cable module and DUT might be grounded through wires depends on different test configurations.

DUTCharge Cable Module

Oscilloscope CDE Test Controller

GND wires

CDE Calibration Waveform – Charge Module ungrounded, Short

Short

Line 4 is in through mode, line 5 is pre-charged to 500V then discharge. We expect high ESD current from line 5 to line 4 on the 100 Ohm transmission line to be 500V/100 Ohm = 5A.(DC resistance of each 100 m wire is 25 Ohm, CT-1 current probe cut off frequency is 25 KHz)

On the CH2 waveform, the peak is about 250 mV ( which gives 250 mV X 20 A/V = 5 A. The CH4 waveform is about the reverse of CH2 as current running from line 5 to line 4. The waveform shows significant loss due to the length of the cable. After it reach 2 times the cable length ( the reflection occurs at the ends of the transmission line and several reflection happens until loss attenuated the overall signal.

100 meter CAT5E S/UTP

line 5

line 4

500V GND

5K

5K

CDE Calibration Waveform – Charge Module grounded, Short

Short

When the charge unit shielding layer is grounded, the common mode impedance of the charged line is lowered and the capacitance of the charged line is significantly increased, therefore we should see increase of the voltage discharge waveform on CH1 and CH3.

Comparing to previous case, the discharge waveform voltage vs GND is increased a lot (due to capacitance increase). The large capacitor discharge is through the two 5 k Ohm resistors.


line 5

line 4

500V GND

GND Connect

5K

5K

CDE Calibration Waveform – Charge Module grounded, Open

OPEN

When DUT is open, very little current is expected, only a short duration of high displacement current happened at the very beginning .The open voltage is expected to be 500V.

The voltage peak of CH1 is about 490 mV * 1010 = 494.9 V, same as previous case

The charge will discharged from line 5 to ground and the resistive path of the voltage probes.


line 5

line 4

500V GND

GND Connect

5K

5K

CDE Calibration Waveform – Charge Module and 50 ohm grounded, Load

LOAD


line 5

line 4

500V GND

GND Connect

GND ConnectTo the center

of two 50 ohm res

GND

At this case, the center of the 100 Ohm load (between 2 50 Ohm resistors) is connected to CDE ground as current return.

If the load has ground, then the common mode current will run through the load as return quickly.

5K

5K

Probing Delay of the LAN cable from CDE tester to DUT – Internal cable + open

OPEN


line 5

line 4

500V GND

GND Connect

GND ConnectTo the center

of 2 50 ohm res

0.3 m Cable inside CDE Tester

Because the relay is build inside CDE controller, the current measurement at the very beginning (in the ns range ) is not the CDE current for the DUT, but the current for an extension LAN Cable.

Open !

5K

5K

Effect of the LAN cable to DUT– Internal cable + external cable + open

LOAD


line 5

line 4

500V GND

GND Connect


3 meter Cable outside of CDE Tester

After a 2 meter extension cable is connected, the waveform of discharging this LAN is observed before a open load is reached.

Open, start of the DUT measurement

5K

5K

Effect of the LAN cable to DUT– Internal cable + external cable + DUT

LOAD


line 5

line 4

500V GND

GND Connect

GND Connect to the center of 2 50 ohm resistor terminal


3 meter Cable outside of CDE Tester

DUT response started

5K

5K

10/100 Mbs LAN DUT

Transformer center tab connects to a 75 Ohm resistor and then to a HV capacitor to chassis GND.

HV Caps

Transformers

PHY

75 Ohm resistors

PHY

Connector

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CDE Sequence Discharge with 2 DUTs

Two DUTs are tested for 4 wires (two pairs) discharge sequence in this test.

DS108 is an earlier model network switch from NETGEAR, FS108 is a newer model (currently on the market).

NETGEAR DS108 NETGEAR FS108

CDE Waveform with Discharge Sequence Control – 1st Discharge

The first wire (pin 5) discharges while other wires are disconnected

When all other wires are disconnected, the discharge is a common mode current discharge from the charged cable through the DUT and returns though chassis ground & AC ground. The overall current is low due to a common mode choke and the high impedance of the intended ground path.

3A peak, but current afterwards is decreased due to relatively

large common mode impedance


2.6 A peak, but current afterwards is decreased due to

large common mode impedance

CDE Waveform with Discharge Sequence Control – 2nd Discharge

The second wire (pin 4) discharges while the other wire in the pair is connected (pin 5), remaining wires are disconnected.

When the other wire in the pair is connected, the discharge current is mainly flowing in differential mode (between the discharging wire and the previously discharged wire). And because the discharge path has a well-matched impedance, the discharge current is relatively high and long in duration with multiple reflections related to the cable length. The DUT present a “short” load, might because of internal ESD protection turn on.

The observation for this discharge is that, after the first discharge, the capacitance of all other wires are increased a lot after the first wire connection to DUT, so the voltage difference between all other wires and DUT are significantly deceased. Plus, each previous discharge will normally charge up the HV Capacitor connected with the DUT transformer, this will also reduce the voltage potential between other un-connected wires and DUT transformer.

NOTE: This test was done with 10 M Ohm DUT discharge path constantly connected during discharge event. With implement of DUT discharge path control relay, the differential discharge current will be reduced.

1.9 A max, with long duration of high

discharge current



discharge current

CDE Waveform with Discharge Sequence Control – 3rd Discharge

The third wire (pin 3) discharges while one of the wires in the pair (pin 4 or 5) is connected, the remaining wire in the same pair is not connected.

This discharge current path, which has relatively low impedance and current, mainly returns through the two connected wires. There should be some current returning through the common mode path.

This event produces ESD current and is long in duration.

NOTE: This test was done with 10 M Ohm DUT discharge path constantly connected during discharge event. With implement of DUTdischarge path control relay, the differential discharge current will be reduced.


discharge current


1 A max, with long duration of high

discharge current

CDE Waveform with Discharge Sequence Control – 4th Discharge

The last wire (pin 6) discharges while all of the other wires (pin 3, 4 & 5) are connected.

This discharge current path, which also has a well-matched impedance and current, returns mainly through the connected wire in the same pair. The return current through the other two wires is very low.

This event produces ESD current long in duration with multiple reflections related to the cable length.

NOTE: This test was done with 10 M Ohm DUT discharge path constantly connected during discharge event. With newer hardware, the differential discharge current will be reduced.

1 A max, with long duration of high discharge current


1 A max, with long duration of high discharge current

DUT HV Capacitor Charged up during CDE discharge

Each wire of the cable has large capacitance to ground, when they connect to DUT termination with sequence, the redistribution of the charge

between them happens while each wire is contacting the 75 Ohm/1nF Load.

This 100 meter S/UTP cable module has (measured with RCL meter) about 7.5 nFcapacitance between each wire to ground, 5.6 nF between 2 wires in twisted pair, 4.2 nFbetween 2 wires that is not twisted (these include self-capacitance and mutual capacitance) After all wires are connected to DUT, total capacitance to ground is about 27 nF with the internal 1nF HV capacitor.

Connect

DUT HV Capacitor Charged up during CDE discharge

Test setup:S/UTP cable module is charged up to 100V, discharge sequence set to 1-2-3-4-5-6-7-8, 100M Ethernet Common Terminations.

We can see for this test setup, the voltage of HV capacitor after first discharge increased to about 90% of cable charge voltage, this makes the following discharges to have much less voltage difference between charged cable and DUT magnetic wire. The worst discharge is clearly the first pin contact. However, 2 new thoughts from here:1. With no resistive path in parallel with the HV capacitor to ground, voltage between LAN cable and ground can stay high for

a long time after plug in, and the cable can still get charged while it is moving over the floor. LAN cable with one end connected to a grounded device doesn’t guarantee the voltage on the wire to be safe !

2. The discharge RC time constant on the DUT side influence the 2nd – 8th wire discharge potential, if the DUT has resistive path that is small, the second wire discharge (especially if it is a pair with first discharge wire) can create high current.

Older setup with 8 of 10 M Ohm resistors and 10M passive probe

connected between output wires and GND during discharge

New setup, with only 10M passive probe connected between HV Cap and DUT transformer ground during

discharge, and keep discharge relay closed for 1 sec

Capacitance to GND increases after each wire

gets discharged (RC time changes)

After first wire discharge, the voltage difference

between all other wires and DUT transformer ground is

very small.

Manual Twisted Pair Discharge (From Yuling – Cisco)

Test setup:A 200 m cable is charged up to 2kV, only one pair is build into a RJ45 connector and manually push into a PoE device.(no cable arrangement picture, cable might be not relatively far from ground)

In this test, first pin contact creates largest discharge current – > 10 AThe second pin contact discharge is captured with relatively large current, however, the current runs on the pair is not symmetric, indicating this device has small or no common mode rejection device.The delay between first discharge and second discharge is about 2ms.

Ethernet Terminal (For reference)

Ethernet twisted pairs are usually terminated with 75 Ohm resistor and 2kV capacitors to GND for common mode. And for differential mode, it is terminated 100 ohm.

Below is a schematic from TI AN-1263 (www.ti.com/litv/pdf/snla056d )

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Ethernet Magnetics and Common Mode Chuck (For reference)

The magnetics and common mode chuck of the Ethernet termination not only has large impact on PHY performance, but also has impact on the EMI and ESD. Below is a magnetics from TI AN-1263 (www.ti.com/litv/pdf/snla056d )

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LAN Cable Wiring Definitions (For reference)

http://en.wikipedia.org/wiki/568B

http://en.wikipedia.org/wiki/Ethernet_crossover_cable

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http://en.wikipedia.org/wiki/568B

http://en.wikipedia.org/wiki/Ethernet_crossover_cable

LAN Cable Twisted Pair Types (For reference)

Most Common

Second Common

http://en.wikipedia.org/wiki/Twisted_pair

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http://en.wikipedia.org/wiki/Twisted_pair

Engineering

ESDEMC CDE IEEE Symposium 2014