SEMICONDUCTOR INTEGRATED CIRCUITS

A 6.25 Gb/s equalizer in 0.18 μm CMOS technology for high-speed SerDes

Mingke Zhang and Qingsheng Hu

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 Corresponding author: Hu Qingsheng, Email:qshu@seu.edu.cn

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Abstract: This paper presents a 0.18 μm CMOS 6.25 Gb/s equalizer for high speed backplane communication. The proposed equalizer is a combined one consisting of a one-tap feed-forward equalizer (FFE) and a two-tap half-rate decision feedback equalizer (DFE) in order to cancel both pre-cursor and post-cursor ISI. By employing an active-inductive peaking circuit for the delay line, the bandwidth of the FFE is increased and the area cost is minimized. CML-based circuits such as DFFs, summers and multiplexes all help to improve the speed of DFEs. Measurement results illustrate that the equalizer operates well when equalizing 6.25 Gb/s data is passed over a 30-inch channel with a loss of 22 dB and consumes 55.8 mW with the supply voltage of 1.8 V. The overall chip area including pads is 0.3×0.5 mm2.

Key words: feed-forward equalizer (FFE)decision feedback equalizer (DFE)delay lineactive-inductive peakingcurrent mode logic (CML)



[1]
Dickson T O, Bulzacchelli J F, Friedman D J. A 12 Gb/s 11 mW half-rate sampled 5-tap decision feedback equalizer with current integrating summers in 45 nm SOI CMOS technology. IEEE J Solid-State Circuits, 2009, 44(4):1298 doi: 10.1109/JSSC.2009.2014733
[2]
Song S, Stojanovic V. A 6.25 Gb/s voltage-time conversion based fractionally spaced linear receive equalizer for mesochronous high-speed links. IEEE J Solid-State Circuits, 2011, 46(5):1183 doi: 10.1109/JSSC.2011.2105670
[3]
Beukema T, Sorna M, Selander K. A 6.4-Gb/s CMOS SerDes core with feed-forward and decision-feedback equalization. IEEE J Solid-State Circuits, 2005, 40(12):2633 doi: 10.1109/JSSC.2005.856584
[4]
Maeng M, Bien F, Hur Y. 0.18-μm CMOS equalization techniques for 10-Gb/s fiber optical communication link. IEEE Trans Microw Theory Tech, 2005, 53(11):3509
[5]
Ju Hao, Zhou Yumei, Zhao Jianzhong. A low power CMOS 3.3 Gbps continuous-time adaptive equalizer for serial link. Journal of Semiconductors, 2011, 32(9):095001 doi: 10.1088/1674-4926/32/9/095001
[6]
Li L. Power optimization of an 11.75-Gb/s combined decision feedback equalizer and clock data recovery circuit in 0.18-μm CMOS. IEEE Trans Circuits Syst, 2011, 58(3):441 doi: 10.1109/TCSI.2010.2072190
[7]
Rothenberg B C, Lewis S H. A 20-M samples switched-capacitor finite-impulse-response filter using a transposed structure. IEEE J Solid-State Circuits, 1995, 30(12):1350 doi: 10.1109/4.482161
[8]
Treichler J R, Fijalkow I. Fractionally spaced equalizers. IEEE Signal Processing Magazine, 1996, 13(3):65 doi: 10.1109/79.489269
[9]
Kargar M, Green M M. A 10 Gb/s adaptive analog decision feedback equalizer for multimode fiber dispersion compensation in 0.13μm CMOS. ESSCIRC, 2010:550
[10]
Seong C K, Rhim J. A 10-Gb/s adaptive look-ahead decision feedback equalizer with an eye-opening monitor. IEEE Trans Circuits Syst, 2012, 59(4):209 doi: 10.1109/TCSII.2012.2186366
Fig. 1.  Channel characteristics of 30-inch FR4 backplane.

Fig. 2.  LE equalization principle.

Fig. 3.  DFE block diagram.

Fig. 4.  Block diagram of the proposed equalizer.

Fig. 5.  Active delay line.

Fig. 6.  Simulation result of an active delay cell with a delay of $T$/2.

Fig. 7.  Multiplier & summer.

Fig. 8.  Eye diagrams of summer output with different $b_{1}$. (a) $b_{1}$ $=$ 0.25 (under-equalization). (b) $b_1$ $=$ 0.35 (over-equalization). (c) $b_{1}$ $=$ 0.3 (optimization).

Fig. 9.  MSDFF.

Fig. 10.  CML based MUX.

Fig. 11.  Bandwidth of MUX.

Fig. 12.  Post simulation results of the equalizer @ 6.25 Gbp/s.

Fig. 13.  Photomicrograph of the equalizer.

Fig. 14.  Block diagram of the chip measurement.

Fig. 15.  Measured eye diagram at 5 Gb/s. (a) Before equalization. (b) After equalization.

Fig. 16.  Measured eye diagram at 6.25 Gb/s. (a) Before equalization. (b) After equalization.

Table 1.   Equalizer performance comparisons.

[1]
Dickson T O, Bulzacchelli J F, Friedman D J. A 12 Gb/s 11 mW half-rate sampled 5-tap decision feedback equalizer with current integrating summers in 45 nm SOI CMOS technology. IEEE J Solid-State Circuits, 2009, 44(4):1298 doi: 10.1109/JSSC.2009.2014733
[2]
Song S, Stojanovic V. A 6.25 Gb/s voltage-time conversion based fractionally spaced linear receive equalizer for mesochronous high-speed links. IEEE J Solid-State Circuits, 2011, 46(5):1183 doi: 10.1109/JSSC.2011.2105670
[3]
Beukema T, Sorna M, Selander K. A 6.4-Gb/s CMOS SerDes core with feed-forward and decision-feedback equalization. IEEE J Solid-State Circuits, 2005, 40(12):2633 doi: 10.1109/JSSC.2005.856584
[4]
Maeng M, Bien F, Hur Y. 0.18-μm CMOS equalization techniques for 10-Gb/s fiber optical communication link. IEEE Trans Microw Theory Tech, 2005, 53(11):3509
[5]
Ju Hao, Zhou Yumei, Zhao Jianzhong. A low power CMOS 3.3 Gbps continuous-time adaptive equalizer for serial link. Journal of Semiconductors, 2011, 32(9):095001 doi: 10.1088/1674-4926/32/9/095001
[6]
Li L. Power optimization of an 11.75-Gb/s combined decision feedback equalizer and clock data recovery circuit in 0.18-μm CMOS. IEEE Trans Circuits Syst, 2011, 58(3):441 doi: 10.1109/TCSI.2010.2072190
[7]
Rothenberg B C, Lewis S H. A 20-M samples switched-capacitor finite-impulse-response filter using a transposed structure. IEEE J Solid-State Circuits, 1995, 30(12):1350 doi: 10.1109/4.482161
[8]
Treichler J R, Fijalkow I. Fractionally spaced equalizers. IEEE Signal Processing Magazine, 1996, 13(3):65 doi: 10.1109/79.489269
[9]
Kargar M, Green M M. A 10 Gb/s adaptive analog decision feedback equalizer for multimode fiber dispersion compensation in 0.13μm CMOS. ESSCIRC, 2010:550
[10]
Seong C K, Rhim J. A 10-Gb/s adaptive look-ahead decision feedback equalizer with an eye-opening monitor. IEEE Trans Circuits Syst, 2012, 59(4):209 doi: 10.1109/TCSII.2012.2186366
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    Received: 28 April 2013 Revised: 07 June 2013 Online: Published: 01 December 2013

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      Mingke Zhang, Qingsheng Hu. A 6.25 Gb/s equalizer in 0.18 μm CMOS technology for high-speed SerDes[J]. Journal of Semiconductors, 2013, 34(12): 125010. doi: 10.1088/1674-4926/34/12/125010 M K Zhang, Q S Hu. A 6.25 Gb/s equalizer in 0.18 μm CMOS technology for high-speed SerDes[J]. J. Semicond., 2013, 34(12): 125010. doi: 10.1088/1674-4926/34/12/125010.Export: BibTex EndNote
      Citation:
      Mingke Zhang, Qingsheng Hu. A 6.25 Gb/s equalizer in 0.18 μm CMOS technology for high-speed SerDes[J]. Journal of Semiconductors, 2013, 34(12): 125010. doi: 10.1088/1674-4926/34/12/125010

      M K Zhang, Q S Hu. A 6.25 Gb/s equalizer in 0.18 μm CMOS technology for high-speed SerDes[J]. J. Semicond., 2013, 34(12): 125010. doi: 10.1088/1674-4926/34/12/125010.
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      A 6.25 Gb/s equalizer in 0.18 μm CMOS technology for high-speed SerDes

      doi: 10.1088/1674-4926/34/12/125010
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      • Corresponding author: Hu Qingsheng, Email:qshu@seu.edu.cn
      • Received Date: 2013-04-28
      • Revised Date: 2013-06-07
      • Published Date: 2013-12-01

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