A 32Gb/s Wireline Receiver with a LowFrequency Equalizer, CTLE and 2-Tap DFE
in 28nm CMOS [1]
Custom Implementation of DSP Systems
Rasool Faraji
S.R.Faraji@ut.ac.ir
University of Tehran
College of Engineering
School of Electrical and
Computer Engineering
Spring 1392
CONTENT
• Introduction
• Equalization
• ISI
• Channel Characteristics
•
•
•
•
Receiver Architecture
Measurement Results
Technology and Core Areas and Power Consumption
References
Equalization
• Equalization
• ISI
• Equalization implementations
o
o
o
o
TX FIR (FFE)
RX FIR
RX CTLE
RX DFE
Fig. 1. Frequency response of the channel and equalizer[5]
• Characteristics
o
o
o
o
Reduce the ISI
Reduce the BER
Improve the high frequency losses
Improve the low frequency losses
Fig. 2. Eye Diagrams befor and after Equalization[6]
Channel Characteristics
•
Channel Characteristics
o Channel loss at very low frequencies
is dominated by the skin effect
o Rest of the channel loss is mainly due to the
material properties i.e. dielectric loss
o Low-frequency loss has a very gentle slope
o Conventional equalizers such as CTLE and FFE
have a 20dB/dec slope which doesn’t match
 A new type of equalizer is needed with a gentler
equalization slope
Fig 3. Channel Loss [10]
Fig 4. Channel Response [6]
Receiver Architecture
•
•
•
•
•
•
•
•
•
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Input-Termination Network
2-Tap Speculative DFE
CTLE
LFEQ
Boundary Sampler
Clock Recovery
Equalizer Adaptation
Phase Interpolator
CML to CMOS
DDC
Fig 5. Receiver block diagram [1]
Receiver Architecture
• Two-tap Speculative DFE
•
•
•
Boundary Sampler
Error Sampler
Linaer Transconductor Circuit(LTC)
Fig 6. Data path with two-tap speculative DFE, boundary and error path [1]
Receiver Architecture
• CTLE Implementation
•
•
•
Improve the high frequency losses
Provides large boost (0 to 15dB) at high frequencies
CTLE and speculative 2-Tap DFE reduce ISI due to dielectric loss
Fig 7. CTLE Implementation [1]
Receiver Architecture
• Low-Frequency Equalizer (LFEQ)
•
•
•
Improve the low frequency losses
An equalizer with a closely
placed zero and pole
approximates the
gentler slope
Implements a small amount
of equalization (0 to 4dB) to
compensate for the gentle
slope of the low frequency
Fig 8. low-frequency equalizer Implementat ion[1]
Measurement Results
• Improve the Low frequency losses
• Jitter (DDJ) improved from 0.42UI to 0.21UI with the LFEQ
Fig 9. Frequency-domain and time-domain responses of a backplane channel with and without low frequency equalization [1]
Measurement Results
• BER improved from 10−7 to <10−12 with
37dB loss at 16GHz (40dB total loss with
receiver package)
Fig 10. Channel Insertion Loss [1]
Fig 11. 32Gb/s PRBS31 Bathtub Curve [1]
Measurement Results
• RX Differential Return Loss
•
better than 10dB from 0 to 20GHz
Fig 12. Receiver′s differential input return loss measurement [1]
Technology and Core Areas and
Power Consumption
•
•
•
•
28 nm CMOS Technology
0.9 V supply
Area: 1200μm x 275μm
Power: 240mW
Fig 13. Chip micrographs [1]
References
[1] Parikh,S,Kao.T, Hidaka.Y,Jian Jiang, Toda.A, Mcleod.S, Walker.W, Koyanagi.Y, ShibuyaT,
Yamada.J,“A 32Gb/s Wireline Receiver with a Low-Frequency Equalizer, CTLE and 2-Tap
DFE in 28nm CMOS,” in ISSCC Dig. Tech. Paper.s, pp. 29-28, Feb 2013.
[2] J. Bulzacchelli et al., “A 28Gb/s 4-Tap FFE/15-Tap DFE Serial Link Transceiver in 32nm
SOI CMOS Technology,” in ISSCC Dig. Tech. Papers, pp. 324-325, Feb 2012.
[3] J. Savoj, et al., “A Wide Common-Mode Fully-Adaptive Multi-Standard 12.5Gb/s Backplane
Transceiver in 28nm CMOS,” in VLSI Circuits Dig. Tech.Papers, pp.104-105, June 2012.
[4] Y. Hidaka, et al., “A 4-Channel 10.3Gb/s Transceiver with Adaptive Phase Equalizer for 4to-41dB Loss PCB Channel,” in ISSCC Dig. Tech. Papers, pp.346-347, Feb 2011.
[5] Y. Hidaka, et al., “A 4-Channel 1.25-10.3Gb/s Backplane Transceiver Macro With 35dB
Equalizer and Sign-Based Zero-Forcing Adaptive Control,” IEEE J. Solid-State Circuits, vol.
44, no. 12, pp.3547-3559, Dec. 200.
[6] Sam Palermo Analog & Mixed-Signal Center Texas A&M University.“ Lecture 7:
Equalization Introduction & TX FIR Eq “, ECEN720: High-Speed Links Circuits and
Systems Spring 2013.
Thank You