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Magnetics forHigher DC Imbalance

Brian BuckmeierBel Stewart Connector

IEEE P802.3atDTE Power Enhancements Task Force

Denver, COMarch 6 - 10, 2006

IEEE P802.3at DTE Power Enhancements Task Force 2

Topics• 10/100/1000Base-T backward

compatible• Targeted 24mA and 34mA DC imbalance• Electrical parameters measured:• Insertion loss, Return Loss, OCL with DC

bias• Component power dissipation and

temperature rise• Distortion of Insertion Loss and Return

Loss with power applied• Component size increase, single port

and multi-port components

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Schematic and Electrical Parameters• 1000Base-T circuit used for backward compatibility• Two pairs used for calculations, worst case scenario• Tested with 700mA of current

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Insertion Loss• Insertion Loss without 700mA of current

applied to center tap of transformer

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Insertion Loss• Insertion Loss without 700mA• Plot shows IL Test Fixture distortion

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Insertion Loss• Insertion Loss with 700mA

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Insertion Loss• Test circuit, no power• Plot shows Imbalance Test Fixture distortion

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Insertion Loss• Insertion Loss with 26mA imbalance = 337 mA

one leg, 363 mA other leg

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Insertion Loss - Conclusions

• Insertion Loss does not distort with 700mA• Insertion Loss does not degrade using

magnetics for 24 mA imbalance design

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Return Loss• Return Loss 100 Ohms without 700mA of

current applied to center tap of transformer

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Return Loss• Return Loss 115 Ohms without 700mA of

current applied to center tap of transformer

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Return Loss• Return Loss 85 Ohms without 700mA of

current applied to center tap of transformer

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Return Loss• Return Loss without 700mA, 100 Ohms• Plot shows RL Test Fixture distortion

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Return Loss• Return Loss with 700mA, 100 Ohms

•85 Ohms and 115 Ohms are the same with and without 700mA

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Return Loss - Conclusions

• Return Loss does not distort with 700mA• Return Loss does not degrade using

magnetics for 24 mA imbalance design• Return Loss still meets IEEE 802.3

10/100/1000Base-T specifications

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Phase• Phase with 700mA of current applied to

center tap of transformer

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Phase• Phase with DC imbalance of 26mA• Conclusion: Phase does not distort with

700mA

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OCL

37739842144647349952170° C

55256658059360661762825° C

4834904955085165235350° C

OCL26mA

µH

OCL25mA

µH

OCL24mA

µH

OCL23mA

µH

OCL22mA

µH

OCL21mA

µH

OCL20mA

µH24mA Design

• 24mA design over temperature with bias• Designed for 50µH of margin

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OCL

40542446344852170° C

74378983788693525° C

6686756907277600° C

OCL 34mAµH

OCL 33mAµH

OCL 32mAµH

OCL 31mAµH

OCL 30mAµH34mA Design

• 34mA design over temperature with bias• Designed for 50µH of margin

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Component Power Dissipation vs. Temperature, CalculatedPower Dissipated By Component vs. Operating Temperature, 700mA

0.118

0.115

0.112

0.109

0.106

0.103

0.100

0.097

0.094

0.091

0.000 0.020 0.040 0.060 0.080 0.100 0.120 0.140

25

30

35

40

45

50

55

60

65

70O

pera

ting

Tem

p (°

C)

Power Dissipated By Components (Watt)

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Component Temperature Rise vs. Operating Temperature,Calculated

Operating Temperature vs. Component Temperature Rise, 700mA

4.64.7

4.95.0

5.25.3

5.55.6

5.85.9

0

10

20

30

40

50

60

70

80

4.6 4.7 4.9 5.0 5.2 5.3 5.5 5.6 5.8 5.9Component Temp. Rise (°C)

Ope

ratin

g Te

mp.

(°C

)

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Component Temperature Rise vsOperating Temperature Measured

• Measured temperature rise of component using 800mA,probe molded into center of magnetics winding area

• Minimal rise seen using 700mA, so increased to 800mA

72.3° C

27.7° C

2.4° C

800mA TemperatureRise0mA

DC Bias

2.9° C69.4° C70° C

2.6° C25.1° C25° C

1.9° C0.5° C0° C

OperatingTemperature

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Component Size IncreaseDepth Only

% IncreaseDescription

10%

0%

15%

0%

24mA

20%Multi-port, two-pair, 10/100/1000Base-T

0%Multi-port, 10/100Base-T

20%Single port, 10/100/1000Base-T

0%Single port, 10/100Base-T

34mA

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Conclusions

• 1000Base-T backward compatiblemagnetics are capable ofsupporting 24mA of DC bias

• Distortion with DC bias is not anissue

• Temperature rise is ~ 6° C whenoperating at 70° C and applying800mA of current per port

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Future Work

• Different circuit topologies need tobe tested

• 1000Base-T backward compatiblemagnetics are capable ofsupporting 34mA of DC bias butrequire further test validation.Insertion Loss, Return Loss anddifferent circuits topologies.

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Thank you for your time