Timothy O. Dickson and Sorin P. Voinigescu

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Low-Power Circuits for a 2.5-V, 10.7-to-86-Gb/s
Serial Transmitter in 130-nm SiGe BiCMOS

• Timothy O. Dickson and Sorin P. Voinigescu
• Edward S. Rogers, Sr. Dept of Electrical and
  Computer Engineering
• University of Toronto
• CSICS
• November 15, 2006

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Outline

• Motivation
• High-speed, low-power design techniques
• 2.5-V, 80-Gb/s BiCMOS Transmitter
• Measurement results
• Conclusions

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Next Generation High-Speed Wireline 100-Gb/s
Ethernet
New design challenges as fundamental frequencies
enter mm-wave regime
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Power Consumption
should consume less power than
100 Gb/s
10 x 10 Gb/s
State-of-the-art High-Speed Transceivers
Technology 130-nm CMOS SiGe (120-GHz fT)
Data Rate 3.125-to-10.7-Gb/s 2.7-to-43-Gb/s
Integration Single-chip Chip set
Power consumption 800 mW 12 W
Reference Aeluros, ISSCC 2004 Big Bear, ISSCC 2003
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Power Consumption
should consume less power than
100-Gb/s 41 MUX?
Technology SiGe (210-GHz fT)
Data Rate 132-Gb/s
Supply Voltage -3.3V
Power consumption 1.45 W
Reference IBM, ISSCC 2004
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MOSFETs vs HBTs

• HBT _at_ peak-fT VBE 900mV and does not scale!
• 130-nm nMOS _at_ peak-fT VGS 750mV and
  decreasing!

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Power reduction techniques
43-GHz latch consumes only 20mW
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Transmitter Block Diagram
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2.5-V, 87-Gb/s BiCMOS Selector
86-Gb/s selector consumes 60mW
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2.5-V, 80-Gb/s BiCMOS Pre-Emphasis Driver

• MOS gm and input capacitance relatively constant
  as bias current changes.
• Excellent for output stages with adjustable
  amplitude control.

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2.5-V, 80-Gb/s BiCMOS Pre-Emphasis Driver
130-nm MOSFETs switching at 80-Gb/s!
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2.5-V, 80-Gb/s BiCMOS Pre-Emphasis Driver

• Adjustable pre-emphasis for operation up to
  80-Gb/s
• Boosts high-frequency content to compensate for
  line losses.
• Output match S22 lt -10dB up to 94 GHz.

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36-43 GHz Colpitts VCO
-105 dBc/Hz _at_ 1-MHz offset

• SiGe HBTs used as negative resistance generators.
• Differential tuning to reject common-mode noise.
• Maximize tank swing, bias HBTs at NFMIN for low
  phase noise

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Die Photograph
PLL
1.5 mm
PRBS 84 MUX
41 MUX Output Driver
1.8 mm
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Measured Results 80-Gb/s

• Running for more than 1 hour continuously in the
  lab.
• Jitter 560 fs (rms) , Rise/fall time 4-5 ps,
  Amplitude 300 mV

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Verification of Correct Multiplexing
Using pattern capture capabilities of the
Agilent 86100C DCA
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Verification of Correct Multiplexing
Examine the tone spacing using Agilent E4448A PSA
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80-Gb/s Amplitude Control
Little degradation in eye quality as amplitude
varies from 100mV to 300 mV per side
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Maximum Data Rate 87-Gb/s
685 MHz
87 GHz
685 MHz
127
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Maximum Data Rate vs. Temp.
92-Gb/s _at_ 0oC
71-Gb/s _at_ 100oC
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Comparison
Technology fT/fMAX Data Rate Supply Voltage Power
130-nm CMOS 85/90 GHz 40-Gb/s (half-rate) 1.5 V 2.7 W
InP HBT 150/150 GHz 43-Gb/s (full-rate) -3.6/ -5.2 V 3.6 W
180-nm SiGe BiCMOS HBT 120/100 GHz 43-Gb/s (half-rate) -3.6 V 1.6 W
180-nm SiGe BiCMOS HBT 120/100 GHz 43-Gb/s (full-rate) -3.6 V 2.3 W
130-nm SiGe BiCMOS MOS 85/90 GHz HBT 150/150 GHz 87-Gb/s (half-rate) 2.5 V 1.36 W
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Conclusions

• Described methods for power reduction in
  high-speed building blocks.
• Use BiCMOS topology to lower supply voltage.
• Trade off bias current for inductive peaking.
• Applied these principles to the design of the
  first 87-Gb/s serial transmitter, which consumes
  less power than any 40-Gb/s TX reported to date.
• As compared with state-of-the-art CMOS, this work
  shows that you can achieve double the data rate
  with half the power dissipation simply by adding
  the SiGe HBT option.

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Acknowledgements

• STMicroelectronics Crolles for chip fabrication
• STMicroelectronics, Gennum, CITO, and NSERC for
  financial support
• CMC for CAD tools
• CFI and OIT for equipment and test support

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Questions?
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Backups
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DC Considerations
Need CM resistor in 43-GHz clock buffer
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Future Directions Futher Power Savings

• Reduce supply voltage to 1.8V by removing current
  sources.
• 38 power savings would result in 86-Gb/s TX that
  consumes 825 mW.

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SiGe Building Block Supply Voltage
DC drops dictate at least 3.3-V supply voltage
150 mV IR
900 mV VBE
900 mV VBE
750 mV VCE
600 mV VCE IR
Unlike CMOS, supply voltage does not scale!!
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CMOS vs. SiGe BiCMOS
SiGe HBT has 2-generation speed advantage