single_ended and differential tdr measurement with the aid of
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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
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)
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
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
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
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
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
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
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