reducing jitter utilising adaptive pre-emphasis fir filter for high speed serial links marius goosen...
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Reducing jitter utilising Reducing jitter utilising adaptive pre-emphasis FIR adaptive pre-emphasis FIR filter for high speed serial linksfilter for high speed serial links
Marius GoosenMarius Goosen
Supervisor: Prof. Saurabh SinhaSupervisor: Prof. Saurabh Sinha
Microelectronics & Electronics Group
Friday 21 April 2023
Departement Elektriese, Elektroniese & Rekenaar-IngenieursweseDepartment of Electrical, Electronic & Computer EngineeringKgoro ya Merero ya Mohlagase, Elektroniki & Bointšinere bja Khomphutha
Departement Elektriese, Elektroniese & Rekenaar-IngenieursweseDepartment of Electrical, Electronic & Computer EngineeringKgoro ya Merero ya Mohlagase, Elektroniki & Bointšinere bja Khomphutha
Agenda
• Background• High speed serial links on copper channels• Frequency dependant distortion• Deterministic jitter• Adaptive pre-emphasis• Pilot signaling and peak detection• Simulation results• Experimental results• Conclusion
2
Background
• M-data lines combined into a high speed serial data line• Less skew between lines• Higher bandwidth capability• Lower pin count and cost of implementation
Departement Elektriese, Elektroniese & Rekenaar-IngenieursweseDepartment of Electrical, Electronic & Computer EngineeringKgoro ya Merero ya Mohlagase, Elektroniki & Bointšinere bja Khomphutha
Scramble
Scramble
8B/10B
8B/10B
MultiplexerPre-emphasis
Driver
EqualiserSampler &
DemultiplexerClock / Data
Recovery
D+
D-
D+
D-
m
mm
m
m
Transmitter
Receiver
Encoder
Decoder
3
Departement Elektriese, Elektroniese & Rekenaar-IngenieursweseDepartment of Electrical, Electronic & Computer EngineeringKgoro ya Merero ya Mohlagase, Elektroniki & Bointšinere bja Khomphutha
High speed serial links
Reference Data rate Technology Pre-emphasis
[1] 1 Gb/s CMOS None
[2] 5 Gb/s CMOS 3-tap
[3] 10 Gb/s CMOS 5-tap
[4] 10 Gb/s BiCMOS None
[1] C.Y. Yang and Y. Lee, “A 0.18 μm CMOS 1 Gb/s serial link transceiver by using PWM and PAM techniques”, IEEE International Symp. on Circuits and systems, Vol. 2, pp. 1150-1153, Kobe, 23-26 May 2005.
[2] C.H. Lin, C.H. Wang and S.J. Jou, “5 Gbps serial link transmitter with pre-emphasis”, IEEE Proc. of the 2003 Asia South Pacific design automation conf., Kitakyushu, pp. 795-800, 21-24 Jan. 2003.
[3] M. Li, T. Kwasniewski, S. Wang and Y. Tao, “A 10 Gb/s transmitter with multi-tap FIR pre-emphasis in 0.18μm CMOS technology”, IEEE Proc. of the 2005 Asia South Pacific design automation conf., Shanghai, pp 679-682, 18-21 Jan. 2005.
[4] D.J. Friedman, M. Meghelli, B.D. Parker, J. Yang, H.A Ainspan, A.V. Rylyakov, Y.H. Kwark, M.B. Ritter, L. Shan, S.J. Zier, M. Soma and M. Soyuer, “SiGe BiCMOS integrated circuits for high speed serial communication links”, IBM J. Res. & Dev., Vol 47, No 2/3, Mar. 2003.
4
Frequency dependant distortion: Package parasitics
• Introduces frequency dependant devices
5
Departement Elektriese, Elektroniese & Rekenaar-IngenieursweseDepartment of Electrical, Electronic & Computer EngineeringKgoro ya Merero ya Mohlagase, Elektroniki & Bointšinere bja Khomphutha
Cpad_sub CPCBpad_GP
LBondwire
Inductance a problem:• Thicker bond wires• Use multiple bond wires• Use tape bonding≈ 45-50 fF
≈ 1 nH/mm
Frequency dependant distortion: Copper backplane channel ●
• Copper channel loss:
• Conductor loss due to skin effect:
• Where Rskin represents a frequency dependent resistor attenuating the signal:
• Loss due to dielectric:
Departement Elektriese, Elektroniese & Rekenaar-IngenieursweseDepartment of Electrical, Electronic & Computer EngineeringKgoro ya Merero ya Mohlagase, Elektroniki & Bointšinere bja Khomphutha
dctot
f
Rskin
tan
1
1
r
r
eff
effd c
f
6
wZ
R
o
skinc 686.8
Frequency dependant distortion: Copper backplane channel ● ●
7
108
109
1010
1011
0
5
10
15
20
25
Frequency [Hz]
Lo
ss [d
B/m
]
Conductor lossDielectric lossTotal loss
Departement Elektriese, Elektroniese & Rekenaar-IngenieursweseDepartment of Electrical, Electronic & Computer EngineeringKgoro ya Merero ya Mohlagase, Elektroniki & Bointšinere bja Khomphutha
Departement Elektriese, Elektroniese & Rekenaar-IngenieursweseDepartment of Electrical, Electronic & Computer EngineeringKgoro ya Merero ya Mohlagase, Elektroniki & Bointšinere bja Khomphutha
Frequency dependant distortion: Channel response
• Loss of 50 dB @ 10 GHz• Severe frequency dependent distortion
8
0.2 0.4 0.6 0.8 1.00.0 1.2
0.01
0.02
0.03
0.00
0.04
Time [ns]
Vol
tage
[V]
Departement Elektriese, Elektroniese & Rekenaar-IngenieursweseDepartment of Electrical, Electronic & Computer EngineeringKgoro ya Merero ya Mohlagase, Elektroniki & Bointšinere bja Khomphutha
Deterministic jitter
• Deterministic jitter:– Duty cycle distortion– Data dependent jitter
• DDJ caused by this frequency dependent distortion• DDJ causes uncertainty in pulse edges
9
222
1)(
Dt
DttfDJ
Unit interval
Ideal sampling instant
Error
region
Pre-emphasis and implementation
Departement Elektriese, Elektroniese & Rekenaar-IngenieursweseDepartment of Electrical, Electronic & Computer EngineeringKgoro ya Merero ya Mohlagase, Elektroniki & Bointšinere bja Khomphutha
10
ITAP0ITAP1 ITAPN
Adaptive pre-emphasis
11
Departement Elektriese, Elektroniese & Rekenaar-IngenieursweseDepartment of Electrical, Electronic & Computer EngineeringKgoro ya Merero ya Mohlagase, Elektroniki & Bointšinere bja Khomphutha
• Conventional pre-emphasis– Externally adjustably filter taps– Fixed filter taps
• Adaptive pre-emphasis– Automatically finds optimal filter taps– Does not require a characterised channel
Requires characterised channel
Pilot signaling and peak detection ●
12
Departement Elektriese, Elektroniese & Rekenaar-IngenieursweseDepartment of Electrical, Electronic & Computer EngineeringKgoro ya Merero ya Mohlagase, Elektroniki & Bointšinere bja Khomphutha
Initialise h(n) to maximum
Error < 0
Update h(n) by decreasing with
LSB
Transmit pilot signal P(n)
Peak detection at receiver
Error calculation
YesNo
Reset all filter taps
n +1
0 1 2 3 4 5
P(0)
0 1 2 3 4 5
P(1)
0 1 2 3 4 5
P(2)
0 1 2 3 4 5
P(3)
Pilot signaling and peak detection ● ●
• Representing the channel and FIR filter as impulse response
• For the first pilot signal:
• For the second pilot signal:
13
Departement Elektriese, Elektroniese & Rekenaar-IngenieursweseDepartment of Electrical, Electronic & Computer EngineeringKgoro ya Merero ya Mohlagase, Elektroniki & Bointšinere bja Khomphutha
N
kkCHN kncnI
0
N
kkFIR knhnI
0
],,,[ 30201000 chchchchny
2113201012100110000 ,,, cchcchcchcchchcchchny
Design and implementation overview
14
TX RX
D-
D+Data in
CLK in
Departement Elektriese, Elektroniese & Rekenaar-IngenieursweseDepartment of Electrical, Electronic & Computer EngineeringKgoro ya Merero ya Mohlagase, Elektroniki & Bointšinere bja Khomphutha
FIR pre-emphasis
driver
Pilot signal generator
Control logic
CML multiplexer
CML DFF CML XOR
6-bit current mode DAC
Filter tapNo. 1
7-bit counter
Control logic
50 Ω termination
Differential amplifier
Comparator
Pulse generators
7 μA / 0.35 mV
ROMParallel
load shift register
3-bit counter
CMOS control logic
CML multiplexer
Mathematical simulation results ●
15
Departement Elektriese, Elektroniese & Rekenaar-IngenieursweseDepartment of Electrical, Electronic & Computer EngineeringKgoro ya Merero ya Mohlagase, Elektroniki & Bointšinere bja Khomphutha
Mathematical simulation results ● ●
16
Departement Elektriese, Elektroniese & Rekenaar-IngenieursweseDepartment of Electrical, Electronic & Computer EngineeringKgoro ya Merero ya Mohlagase, Elektroniki & Bointšinere bja Khomphutha
0 2 4 6 8 10 12 140
0.5
1Ideal data transmitted
Vol
tage
[V
]
0 2 4 6 8 10 12 140
0.02
0.04Data received without pre-emphasis
Vol
tage
[V
]
0 2 4 6 8 10 12 140
0.05
0.1Data received with pre-emphasis
Vol
tage
[V
]
Bit no.
Mathematical simulation results ● ● ●
17
Departement Elektriese, Elektroniese & Rekenaar-IngenieursweseDepartment of Electrical, Electronic & Computer EngineeringKgoro ya Merero ya Mohlagase, Elektroniki & Bointšinere bja Khomphutha
1 2 3
4 5 6
Departement Elektriese, Elektroniese & Rekenaar-IngenieursweseDepartment of Electrical, Electronic & Computer EngineeringKgoro ya Merero ya Mohlagase, Elektroniki & Bointšinere bja Khomphutha
Circuit simulation results ●
18
1 2
3 4
5 6
Departement Elektriese, Elektroniese & Rekenaar-IngenieursweseDepartment of Electrical, Electronic & Computer EngineeringKgoro ya Merero ya Mohlagase, Elektroniki & Bointšinere bja Khomphutha
Circuit simulation results ● ●
19
0 20 40 60 80 100 1200
1
2
(a)
Vol
tage
(V
)
0 20 40 60 80 100 1200
1
2
(b)
Vol
tage
(V
)
0 20 40 60 80 100 1200
1
2
(c)
Vol
tage
(V
)
0 20 40 60 80 100 1200
1
2
(d)
Vol
tage
(V
)
0 20 40 60 80 100 120
1.5
2
(e)Time (ns)
Vol
tage
(V
)
Departement Elektriese, Elektroniese & Rekenaar-IngenieursweseDepartment of Electrical, Electronic & Computer EngineeringKgoro ya Merero ya Mohlagase, Elektroniki & Bointšinere bja Khomphutha
Experimental results ●
20
1000 μm x 670 μm
340 μm x 160 μm
Approximately 1600 transistors
Area = 0.725mm2
4 mm
4 mm
Experimental results ● ●
21
Departement Elektriese, Elektroniese & Rekenaar-IngenieursweseDepartment of Electrical, Electronic & Computer EngineeringKgoro ya Merero ya Mohlagase, Elektroniki & Bointšinere bja Khomphutha
TX
RX
OUT+
OUT-
Shift IN
Shift OUT
ADJ OUT
EOC IN
CLK
DATA
ADJ OUT
IN- IN+
2 Biasin
g pad
s4 B
iasing p
ads
11 cm
11.5 cm
Experimental results ● ● ●
• Transmitter– Working with a single filter tap– 14 % smaller swing– Unable to move to other states
• Receiver– Pulses generated from TX signals– Correct pulse width – too low amplitude to switch CMOS logic
22
Departement Elektriese, Elektroniese & Rekenaar-IngenieursweseDepartment of Electrical, Electronic & Computer EngineeringKgoro ya Merero ya Mohlagase, Elektroniki & Bointšinere bja Khomphutha
ADJ SFT240 250 260 270 280 290 3000
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
Time [ns]V
olta
ge (
V)
ADJUST
SHIFT__IN
Experimental results ● ● ● ●
• Pulse generation circuit depends on an RC time constant– Used in a feedback loop– R determines:
• Charge rate• Discharge rate
– R Biased PMOS transistor• Achieve constant charge and discharge rate• Too slow, hence CMOS output buffer not properly switched.• Corner analysis
23
Departement Elektriese, Elektroniese & Rekenaar-IngenieursweseDepartment of Electrical, Electronic & Computer EngineeringKgoro ya Merero ya Mohlagase, Elektroniki & Bointšinere bja Khomphutha
Experimental results ● ● ● ●
• Static power dissipation– Transmitter
• Power dissipation = 36 mW– Calculated ≈ 32.5 mW (with one active filter tap)
– Receiver• Power dissipation = 19.8 mW
– Calculated ≈ 18 mW
24
Departement Elektriese, Elektroniese & Rekenaar-IngenieursweseDepartment of Electrical, Electronic & Computer EngineeringKgoro ya Merero ya Mohlagase, Elektroniki & Bointšinere bja Khomphutha
Speed Swing Filter taps Power
Simulated 5 Gb/s 300 mV 6 < 70 mW
10 Gb/s 200mV 6 < 70 mW
Conclusion
• Possible “easy” solution for bandwidth problems– One button high speed serial link
• Speed tests still need to be performed• Pulse generation circuit should be redesigned
– Produce higher integrity signal
• 2 international IEEE conference articles– M.E. Goosen, S. Sinha, A. Müller and M. du Plessis, “A low switching time transmitter for high
speed adaptive pre-emphasis serial links,” Proc. of IEEE CAS 2009, pp. 481-484, Sinaia, 12-14 Oct. 2009.
– M.E. Goosen and S. Sinha, “Analysis of Adaptive FIR Filter Pre-emphasis for High Speed Serial Links,” Proceedings: IEEE Africon 2009, 23-26 Sept. 2009, Nairobi, Kenya.
• 1 local conference article– M.E. Goosen and S. Sinha, “Adaptive FIR filter pre-emphasis for high speed serial links,” Proc.
of the South African conf. on semi and superconductor technology (SACSST), Stellenbosch, pp. 37-42, 8-9 April 2009.
• International Journal paper submission
25
Departement Elektriese, Elektroniese & Rekenaar-IngenieursweseDepartment of Electrical, Electronic & Computer EngineeringKgoro ya Merero ya Mohlagase, Elektroniki & Bointšinere bja Khomphutha
Feedback/questions
Marius Goosen
Carl & Emily Fuchs Institute for Microelectronics
Dept. Electrical, Electronic & Computer Engineering
University of Pretoria
Pretoria 0002
Tel: +27-(12)-420-2177
E-mail: mgoosen@ieee.org
26
Acknowledgement
The authors would like to thank ARMSCOR, the Armaments Corporation of South Africa Ltd, (Act 51 of 2003) for sponsoring this study.
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