VARIABLE SWING Optimal Parallel LINKs Minimal Power, Maximal density for parallel links configurations Claudia P. Barrera advisor: fouad kiamilev PhD committee: Allen Barnett guang gao mayra sarmiento. Ph.D. Dissertation Defense. Outline. Outline  Introduction. Motivation. Motivation.
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VARIABLE SWING Optimal Parallel LINKsMinimal Power, Maximal density for parallel links configurationsClaudia P.Barreraadvisor: fouad kiamilevPhD committee:Allen Barnettguang gaomayra sarmiento
Ph.D. Dissertation Defense
Source: Intel Corporation  http://www.intel.com/technology/timeline.pdf
2003 ITRS (International Technology Roadmap for Semiconductors) roadmap for onchip and offchip speed.
Taken from http://www.ieee.org/organizations/pubs/newsletters/leos/oct04/summer.html
POWER SAVINGS
MAXIMUM LINE LENGTH / SPEED
8 – 16mA  TX current
3.5mA  TX current
0.1mA  TX current
CML
LVDS
WhisperBus
Standard
Fixed TX Power
A
B
Communication
If length is long, a high TX
power is OK
But if the distance between
A and B is short, there will be a
Waste of Power.
Data Rate: X
Data Rate: 4X
P
P
SERDES
Serializer  Deserializer
B
A
SERDES
SERDES
P
P
Data Rate: X
Data Rate: 4X
P
P
SERDES
Bandwidth Increment
4X
4X
P
P
A
B
P
P
P
P
4X
4X
Then, what is the problem with parallel links?
1
2
A
B
A
B
A
B
A
Bandwidth Limitation by maximum number of wires that can be routed
w
d
t
h
εr
POWER OPTIMIZATION ALGORITHM
BASED ON AN ACCELERATED BIT
ERROR RATIO (BER) MEASUREMENT
J. Kramer
BER 2
BER 1
Accelerated BER Tester
Power setting 1
Power setting 2
Power set to 3
Power 3 =F(BER1,BER2)
Accelerated BER Tester
1
2
BER increases
1
2
1
2
BER increases
MINIMAL POWER, MAXIMUM DENSITY FOR A PARALLEL LINK
w
t
εr
h
Microstrip
Stripline
Wire Pair
1
2
εr
M
M
Aggressor
Victim
Near End
Far End
Near End
Far End
Vb
Time
RT
Far End noise
Near End noise
RT: Rising Time
TD: Time Delay
Vb
Near End
Far End
TD
Time
RT
2 x TD
C14
C24
C13
C12
C23
C34
1
2
3
4
C11
C22
C33
C44
V1
1
+
Vo=V1V2
2

V2
Advantages:
Tolerance to ground offsets
Low voltage
High immunity to common noise
The problem of crosstalk in differential signaling is that generates a non common noise.
The effect of electromagnetic fields is higher on the closest line
V1V2
(V1+b*Vn)(V2+d*Vn)
d* > b*
V1
V2
Vn
V1
V2
Vn
Differential pair with a quiet line routed closely
Noise effect in a differential pair when an active line is routed closely
C14
Aggressor
Victim
C24
+

+

C13
C23
Transmission lines are linear systems
Superposition can be applied
VV+
VV
VA+
VA
Victim
Aggressor
VA+=VA
VV+=VA+*(C13)+VA*(C14)
VV=VA+*(C23)+VA*(C24)
VV=VV+VV
C14
C24
Using superposition principle…
C13
VV+=VA+*(C13)+VA*(C14)
C23
+VA*(AntiC13)+VA+*(AntiC14)
+

+

VV=VA+*(C23)+VA*(C24)
VA+=VA
VV=VV+VV
AntiC24
+VA*(AntiC23)+VA*(AntiC24)
AntiC14
AntiC23
AntiC13
Output impedance
Characteristic Impedance Zo
Termination
Impedance
BERT
+
AntiC23

AntiCb
AntiC23
+

BERT
Labview Card
Anritsu Digital Data Analyzer
RX
TX
PRBS
Generator
35uA
48uA
63uA
WElement Matrix
6.5mils
4mils
Aggressor
4mils
Victim
5.7 mils
100mm
Anticoupling capacitances performance
Power noise on the victim line is reduced significantly when an anticoupling capacitance is used. The effect of adding the anticoupling capacitors is actually better than spacing the channels by the rule of thumbs given by the literature.
Aggressor
 No anticoupling capacitances
 Effect of anticoupling capacitances in time domain
Victim
 No anticoupling capacitances
 Effect of anticoupling capacitances
140ps
17ps
AntiC13 = AntiC24 = 0.8pF
AntiC14 and AntiC23
Variable
Minimum crosstalk noise power : 0.7mW
Without the anticoupling capacitances: 3.3mW
79% less noise power
Symmetrical response, and minimum crosstalk noise in both channels:
AntiC13 = AntiC24
Variable
AntiC14 = AntiC23
Variable
Minimum crosstalk noise power : 0.4mW
Without the anticoupling capacitances: 3.3mW
87% less noise power
The use of anticoupling capacitances allow routing of high speed paths as close as possible without performance impact.
Each channel is transmitting at 10Gbps using the minimum space allowed by the manufacturer.
Thank you