Single_ended and Differential TDR Measurement

with the aid ofAnsoft’s

Full_Wave_SPICEZhao-Yin Wu (AKA Daniel Wu), Shou-Fang Chen

(949) 341-0106 x225 and x228daniel.wu@AltraBroadband.com

fang@AltraBroadband.com01/06/02

Agenda• Overview for getting the TDR Data

• Overview for Differential Mode and Common Mode

Impedance

• Practical Example with Measurement Data Verified

• SMA Connector Modeling and its Application for Critical

Net Simulation

Overview for the TDR Data?

How to get the TDR data?Pure Modeling: (Field Extractor + SPICE Solver)

Measurement:

Measurement + Math Calculation:

This box could be equivalent circuit fromSPICELINK or S-Parameter from HFSS orEnsemble!!

The tools are fully available for Altra Broadband!!

1. High speed step generator + High Speed Oscilloscope

trise < 15ps

2. Wideband VNA + TDR option

Wideband VNA to get 1 port S_parameter + Full_Wave_SPICE(The purpose of this presentation material!!)

What is the TDR data?

Cha

ract

eris

tic Im

peda

nce

(ohm

)

Time(s)

TDR data should be characteristic impedance vs time!!

50ohmcable

Z0

Z0(t)

Why&How from VNA to TDRWhy?Generally Speaking, in the lab, VNA is more popular than real TDR. Therefore, if we could find a efficient way to get the TDR data from VNA measurement result than we do no have to purchase another TDR setup.

How?# GHz S MA R 50.000000

0.010000 0.994813 -3.004953

0.020000 0.993534 -5.986811

0.030000 0.992128 -8.973242

…………

9.980000 0.624802 141.488164

9.990000 0.623542 139.131339

10.000000 0.622256 136.766395

From VNA #

# S-parameter data for model one_port_bench

#

Nports = 1

Freq_min = 0.0

Freq_max = 1e+010

Npoints = 1001

Zref = 50

#

0 0.999958 -180

0.01 0.99128 -5.067692

0.02 0.98917 -10.100583

0.03 0.98682 -15.140406

…………

9.98 0.43084 -9.583413

9.99 0.43611 -13.602669

10.00 0.44109 -17.565645

# end of file

To Full_Wave SPICE format (*.fws)

Simulate it in Full_Wave_SPICE

How to get the Zo-t curve from V-t?

Det

ecte

d V

olta

ge, V

dec

t(t)

Time(s)

50ohmcable

Z0

Vexcited

Vdetected(t)

GND plane!

How to get the Zc-t curve from V-t? (cont’d)

SPICE.Full_Wave_ theform calculated is which input, at the voltagenode is )(

simulation SPICE thedoing when definableuser is

50)(

)()(

2 ,50

)(2)(

)( )(

)(2)(

)()()(

)()(

)()(

50

)1.....(..........).........()(

ecteddet

ecteddet

ecteddet

0

0ecteddet

ecteddet

0

ecteddet

0

0ecteddet)1(

0

0)(

0

0

ecteddet

tV

V

tVVtV

tZ

VVthenZif

ZtVV

tVtZ

ZtZtZ

VtV

ZtZZtZ

VVtV

ZtZZtZ

tV

tV

VZ

ZVwhere

tVVtV

excited

excitedL

excitedinc

incL

L

L

inc

L

L

inc

incfrom

L

Ltested

inc

reflect

excitedinc

reflectinc

⋅−

=∴

=Ω=

−=⇒

+=⇒

+−

=−

→+−

=Γ=

+=

+=

Θ

Example from VNA to TDR1st, let’s used the Harmonica to generate the virtual measurement data.

50ohm 50ohm Open

Open

68.735ohm

Open Stub

Example from VNA to TDR (cont’d)

2nd, modify the file format of *.s1p into Full_Wave_SPICE format

# GHz S MA R 50.000000

0.010000 0.994813 -3.004953

0.020000 0.993534 -5.986811

0.030000 0.992128 -8.973242

…………

9.980000 0.624802 141.488164

9.990000 0.623542 139.131339

10.000000 0.622256 136.766395

#

# S-parameter data for model one_port_bench

#

Nports = 1

Freq_min = 0.0

Freq_max = 1e+010

Npoints = 1001

Zref = 50

#

0 0.999958 -1800.01 0.99128 -5.067692

0.02 0.98917 -10.100583

0.03 0.98682 -15.140406

…………

9.98 0.43084 -9.583413

9.99 0.43611 -13.602669

10.00 0.44109 -17.565645

# end of file

Manually add file header,ending andDC information!

Example from VNA to TDR (cont’d)

3rd, run the Full_Wave_SPICE to get the voltage waveform at input node.

Vexcited=1

Please use HFSSv8 to createthe 1 port template, and thenexport the correspondentFull_Wave_SPICE bench!

trise < 200ps

Example from VNA to TDR (cont’d)4th, use the waveform calculator to translate the V-t curve into Z0-t curve.

In schematic capture, Result à Calculator à apply [Vdetected(t)/(neg(Vdetected(t)-1))]*Z0

Reflection from open stub(capacitance!)

Reflection from open end !!

Lossy FR4 !! (loss tangent = 0.02)

Overview for

Differential and Common ModeImpedance

Impedance for Differential Pair

The characteristic impedance should be a 2x2 matrix

=

220120

1201100 ZZ

ZZ Z

+=+=

+=+=

+

=

odd

even

m

m

m

m

Z

ivibibiibibi

vavavvavav

ivii

vv

termreflectionii

Zvv

0

00

22112

22111

24132

22111

2

1

2

1

2

10

2

1

Z00Z

become willthen

)& (modal & with )& (node & thereplace weIf

:follows ascurrent line the to voltageline therelatesmatrix impedance sticcharacteri that theRecall

ly.respective ),impedance( mode aldifferenti and )( impedance modecommon fromsuffer willsignals then theally,differentior equally pair aldifferenti theyou If

diffcm ZZexcite

+-

vVcm 1=

1=diffV

+-

+-

1/2 -1/2

What’s the relation between these impedances?

00

,==

==dcm vcm

dcm

vd

ddiff i

vZ

iv

Z

2 , 21

21vv

vvvv cmd+

=−=

Let’s set the differential voltage signal to 1 Volt and zero the common-mode signalThis implies 211 =v 212 −=v

:, and ZZZZ

between ZRelation 220120

1201100 diffcm ZZ

=

( )

+−

+

−=

−

−

−

−=

⇒

=

− 120110

1201102120

2110110120

1201102120

21102

1

2

1

110120

120110 2/12/1

2/11 2/1

2/1ZZ

ZZ

ZZZZZZ

ZZii

ii

ZZZZ

( ) ( ) 2

1

21

1201102

1201101 ∴

−=⇒−=

−=

ZZii

ZZi diff ( )1201102Z ZZdiff −=

Let’s zero the differential-mode voltage and set the common-mode voltage to 1 VoltThis implies 11 =v 12 =v

−−

−=

−

−

−=

⇒

=

120110

1201102120

2110110120

1201102120

21102

1

2

1

110120

120110 1111

11

ZZZZ

ZZZZZZ

ZZii

ii

ZZZZ

∴+

=⇒+

== 2

1

12011012011021 ZZ

iZZ

ii cm

2120110 ZZ

Z cm

+=

Impedance for Differential Pair(cont’d)

+-

vVcm 1=

+-

+-

1/2 -1/2

vVdiff 1=

cmi

cmi

cmi cmi

This slide refer the paper from Ansoft’s AN, “Differential Pair Analysis” by J. Eric Brackenand Tektronixs’ presentation slide, “FibreChannel Interconnect Signal Integrity Measurement and Modeling Methodologies” by Dima Smolyansky, Dima@tdasystems.comand CYPRESS Semiconductor Corporation’s AN, “Termination and Biasing of HOTLinkII™ High-Speed Serial I/O”

Impedance for Differential Pair(cont’d):, and Z,between ZRelation 00 diffcmoddeven ZZ

ZZZZ

220120

120110

ZZZZ

220120

120110

perfectterminator!!

equalto

( )

( )1201100

1201100

0

000

120110page previous from

120110page previous from

0

0

2Z22

//2

2

22

222

//2

22Z

2

ZZ2

2

2Z2

//Z

obtained! be todifficult not that are ,, is,that

SI2DSPICELINK from obtained be could 2

//2

SI2DSPICELINK from obtained be could 22

2//Z

Z

ZZZ

ZZ

Z

ZZ

ZZ

ZZZZZZ

ZZZ

ZZZZ

ZZ

ZZZ

ZZZ

Z

ZRZ

ZZZZZ

ZZZ

Z

ZZ

Z

odda

ba

b

ab

ab

ab

ab

ababdiff

evenbcm

oddb

oddba

ab

ab

odda

bodd

diffbcm

abdiff

bcm

abodd

beven

−=⋅=

⋅=

+

⋅⋅=

+

⋅=

+⋅

==

+===

−⋅⋅

=⇔+

⋅=⇔=∴

+ →←=

− →←=

=

=

R21Za

R19

Zb

R20

Zb

Practical Examplewith

Measurement Data Verified

Single_ended Impedance

Jumpers

1-Port S-parameter for Single_ended TRL

Voltage Waveform Sim and Single_ended Impedance Derivation In FWS

50)(1

)()(

ecteddet

ecteddet ⋅−

=tV

tVtZ L

50ohm RightAngle Connector!

5pins SMAConnector.

Jumper50 ohm single-ended transmission line.

Single_ended Impedance vs Time

0.0

25.0

50.0

75.0

100.0

0.0E+00 5.0E-10 1.0E-09 1.5E-09 2.0E-09 2.5E-09

Time(s)

Sin

gle_

ende

d Im

peda

nce(

ohm

)

TDR Measurement

VNA+Full_Wave_SPICE

Single_ended Impedance Comparison with Real TDR

Differential Impedance

Jumpers

OpenCircuit

Full 2-Port S-parameter for Differential TRL

Full 2-Port S-parameter for Differential TRL(cont’d)

Trise/fall ~ 20ps

Differential modesource impedance

100 ohm

Full Wave SPICE Voltage Waveform Simulation

How to get the Zc(diff)-t curve from V(diff)-t?

SPICE.Full_Wave_ theform calculated is which input, aldifferenti at the voltagenode is )(

simulation SPICE thedoing when definableuser are & ,100)(1

)(1)(

)(1

)(1

1)(2

1)()( -1 then ,1 if

)(2

)()(

)(

)(2)(

)(

)()(

)(

)()(

)(

100 and 1 then ,50 and - ,1set weif

5050

)1.....(..........).........()(

_diffdet

___diffdet

_diffdet_

_0_diffdet

_diffdet_0

_diffdet

_diffdet__

_0__diffdet_

__diffdet_

_0_

_

_

__diffdet

_0_

_0_

_

___diffdet)1(

_0_

_0_

_

_

_0__0

_0

_0

_0

_0_

____diffdet

tV

VVtV

tVtZ

ZtV

tVZ

tV

tVtZVV

ZVtVV

VtVtZ

ZtZ

tZ

V

VtV

ZtZ

ZtZ

V

VVtV

ZtZ

ZtZt

V

tV

ZVZVVV

Z

ZV

Z

ZVVVVwhere

tVVVtV

diffinitialdiffincdiffL

diffdiffdiffLdiffinitialexcited

diffdiffinitialdiffinc

diffinitialdiffL

diffdiffL

diffL

diffinc

diffinitial

diffdiffL

diffdiffL

diffinc

diffinitialdiffincfrom

diffdiffL

diffdiffLdiff

diffinc

diffrefl

diffdiffincfixtureexcitedexcitedexcited

fixrure

fixtureexcited

fixrure

fixtureexcitedincincdiffinc

diffrefldiffincdiffinitial

⋅−+

=∴

⋅−+

=⋅−−

+=∴==

⋅+−

−=⇒

+=

−⇒

+−

=−−

→+−

=Γ=

Ω=====∴

+⋅−

+⋅=−=

++=

+

+−+

−+−+

Θ

Θ

Vo+

Vo-

1.6V

0.9V1.25V

+700mV

-700mV

0V Diff.

Single Ended

Differential SignalVod = Vo+ -Vo- +100mV

-100mV

7.0=+excitedV

7.0−=−excitedV

7.0_ −=diffinitialV

Ex:

100)(1)(1

)(_diffdet

_diffdet_ ⋅

−+

=tVtV

tZ diffL

Differential Impedance Derivation in Full Wave SPICE

50ohm RightAngle Connector!

5pins SMAConnector.

Jumper

Differential Line with 100 ohm impedance!

Differential Impedance vs Time

0

50

100

150

200

0.0E+00 5.0E-10 1.0E-09 1.5E-09 2.0E-09 2.5E-09

Time(s)

Dif

fere

ntia

l Im

peda

nce(

ohm

)

TDR Measurement

VNA+Full_Wave_SPICE

Differential Impedance Comparison with Real TDR

SMA Connector Modelingand

its Applicationfor

Critical Net Simulation

SMAConnector

PECLTermination

DifferentialReceiver

(MC100LVEP16)

LVPECLTermination

AlteraChip

Critical Net Location

TransistorSPICE(from Vendor)

Analysis Strategy

Wire Bonding Lead_frame

Chip Vendor Provided

Uniform Transmission

linesAnsoft SI2D

Via hole

Ansoft SI3D

SPICE Deck for Simulation

ADC_CLKN

11

ADC_CLKP

11

75mil utripW=10.5mil

75mil utripW=10.5mil

137mil diff_line

W=8mil, Gap=8mil

108mil diff_line

W=8mil, Gap=8mil

U25

MC100LVEP16

6

7

8

5

1

2

3

4

/Q

Q

VCC

VEE

NC

D

/D

VBB

Package&

BJT SPICER172

82R

VCC

R173

130R

R521

82R

R523

130R

VCC

V10.85V

utrip utrip

strip180mil diff_line

W=5mil, Gap=5mil

2279mil diff_line

W=8mil, Gap=8mil

utrip80mil utrip

Ball Pads

Ball Pads

ViaVia

Via

591mil diff_line

W=8mil, Gap=8mil

utrip

Where to get the SPICE Model?

ADC_CLKP

11 Modeling from Tektronix TDR measurement

**mil utrip

***mil diff_line

W=8mil, Gap=8mil

Modeling from Ansoft SI2D

Modeling from Ansoft SI2D

U25

MC100LVEP16

6

7

8

5

1

2

3

4

/Q

Q

VCC

VEE

NC

D

/D

VBB

Chip-vendor provided package andtransistor level model (www.onsemi.com)

Modeling from Ansoft SI3D

JumpersSMA Modeling from TDR Measurement

ConnectorModel

Vendor Provided SPICE Model

1(N.C.)

2(+in)

3(-in)

4(VBB)

8(VCC)

5(VEE)

6(-out)

7(+out)

Package Model

TransistorLevel

SPICE ModelESD_PD

ESD_PD

Model from Field Solver

SPICE Simulation ResultClock = 500MHz, termination is added in the default position. (0603 Resistor Pads)

Signal_In+

Signal_In-

VCC in the Chip

VEE in the Chip

Resistor Pad+

Resistor Pad-

Vdiff@Ball_pad

Vdiff@Resistor_Pad

SPICE Simulation Result(cont’d)Clock = 500MHz, termination is added in the Ball_Pads position.(Altera BGA)

Signal_In+

Signal_In-Vdiff@Resistor_pad(but no resistor mounted on)

Vdiff@Ball_Pad

Appendix I: Frequency Range Planning Before VNA Measurement

milsinchesn

tmilttc

tvleff

eff

60006sec1

106.6047)(82.3

394103

82.3 :strip of Lineon Transmissi 50 sAltra'For

910

=→

⋅×≅⋅⋅×

=⋅=⋅=

≈Ω

≈

ε

εµ

Altrain ResolutionDomain Space Achievable

5.16001.0100

1150GHz is Altrain provide couldanalyzer network thefrequency highest theCurrently,

150 ResolutionDomain Space

250025.040

1140 then SSB, means which 20GHz,~0 from sweep weif t,measuremenor HFSSIn

points) FFT of (#:

) (1 :Span Domain Frequency

:Span Domain Time : ResolutionDomain Frequency

: ResolutionDomain Time

50 sAltra'For

≡

≅→===∴

→⇒

====∴

=

==∆

=

∆

≅

Ω

mmmilsnGHzf

t

mils

psnsGHzf

t

GHzftT

Nf

fFFTFrom

DSBfort

f

Tf

t

ss

ss

s

s

s

ss

s

This should be accompanied with high quality flex cable for the VNA.

Reference1. “Differential Pair Analysis” Ansoft’s AN, by J. Eric Bracken2. “Fiber Channel Interconnect Signal Integrity Measurement and Modeling

Methodologies”, Tektronixs’ presentation slide by Dima Smolyansky, Dima@tdasystems.com

3., “Termination and Biasing of HOTLinkII™ High-Speed Serial I/O”, CYPRESS Semiconductor Corporation’s AN

4. “ECLinPS PlusTM SPICE Modeling Kit”, AND8009/D from On Semiconductor, prepared by Senad Lomigora, Paul Shockman

5. Data sheet for MC10LVEP16, MC100LVEP16, “2.5V / 3.3VECL Differential Receiver/Driver”, from On Semiconductor

6. “Impedance test result for Altra’s board”, Daniel Wu, ShouFang Chen from Altra Broadband

7. “From VNA to TDR in Full Wave SPICE”, Daniel Wu, ShouFang Chen from Altra Broadband

8. “Impedance Control and Termination for Differential Pair”, Daniel Wu from Altra Broadband

9. “Critical Net Analysis Report”, Daniel Wu from Altra Broadband