A 32Gb/s Wireline Receiver with a Low-Frequency Equalizer, CTLE and 2-Tap DFE

in 28nm CMOS [1]

Custom Implementation of DSP Systems

Rasool FarajiS.R.Faraji@ut.ac.ir

University of TehranCollege of Engineering

School of Electrical andComputer 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 TX FIR (FFE)o RX FIRo RX CTLEo RX DFE

• Characteristicso Reduce the ISIo Reduce the BERo Improve the high frequency losseso Improve the low frequency losses

Fig. 1. Frequency response of the channel and equalizer[5]

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 effecto Rest of the channel loss is mainly due to the material properties i.e. dielectric losso Low-frequency loss has a very gentle slopeo 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• 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 to <with 37dB loss at 16GHz (40dB total loss with receiver package)

Fig 11. 32Gb/s PRBS31 Bathtub Curve [1]Fig 10. Channel Insertion Loss [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 4-to-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