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A 32Gb/s Wireline Receiver with a Low-Frequency Equalizer, CTLE and 2-Tap DFE in 28nm CMOS [1]

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 Faraji S.R.Faraji@ut.ac.ir. University of Tehran College of Engineering School of Electrical and Computer Engineering Spring 1392. CONTENT.

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A 32Gb/s Wireline Receiver with a Low-Frequency Equalizer, CTLE and 2-Tap DFE in 28nm CMOS [1]

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  1. 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 Faraji S.R.Faraji@ut.ac.ir University of Tehran College of Engineering School of Electrical and Computer Engineering Spring 1392

  2. CONTENT • Introduction • Equalization • ISI • Channel Characteristics • Receiver Architecture • Measurement Results • Technology and Core Areas and Power Consumption • References

  3. Equalization • Equalization • ISI • Equalization implementations • TX FIR (FFE) • RX FIR • RX CTLE • RX DFE • Characteristics • Reduce the ISI • Reduce the BER • Improve the high frequency losses • Improve the low frequency losses Fig. 1. Frequency response of the channel and equalizer[5] Fig. 2. Eye Diagrams befor and after Equalization[6]

  4. Channel Characteristics • Channel Characteristics • Channel loss at very low frequencies is dominated by the skin effect • Rest of the channel loss is mainly due to the material properties i.e. dielectric loss • Low-frequency loss has a very gentle slope • 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]

  5. 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]

  6. 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]

  7. 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]

  8. 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]

  9. 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]

  10. Measurement Results • BER improved from to <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]

  11. Measurement Results • RX Differential Return Loss • better than 10dB from 0 to 20GHz Fig 12. Receiver′s differential input return loss measurement [1]

  12. 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]

  13. 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.

  14. Thank You

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