Presented by: Joydip Das Oct' 21, 2005

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Presentation on Adiabatic Circuits
Presented by Joydip Das Oct. 21, 2005
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Adiabatic Circuits

• Contents
• History of Adiabatic Computing
• Basics of Adiabatic Computing
• Proposed Adiabatic Circuits
• Proposed Clock Generation Circuits
• Integration with Standard CMOS Systems
• My Plans

Presented by Joydip Das on Oct. 21, 2005
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Adiabatic Circuits

• History of Adiabatic Computing
• The first paper Boyd G. Watkins, A low-power
  multiphase circuit technique, IEEE Journal of
  Solid-State Circuits, pp. 213-220, Dec. 1967
• 60s 80s Researches in IBM (Bennett
  Landauer), MIT, Caltech on computational and
  reversible computation
• 1992 Introduction of the term Adiabatic
  Circuits by J. G. Koller and W. C. Athas,
  Adiabatic switching, low energy computing, and
  the physics of storing and erasing information,
  PhysComp 92 Proc. of the Workshop on Physics
  and Computation, Oct 2-4, 1992, Dallas Texas
• 2002 Formation of Adiabatic Logic Ltd., a
  company to deliver adiabatic products services.
  Developed an output driver for ICs that can save
  up to 75 power in inter-chip communications

Presented by Joydip Das - Oct. 21, 2005
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Adiabatic Circuits

• History - Researches
• Mid- Late 90s Koller Athas (USC), Roy
  (Purdue), Oklobdzija (Berkeley), Dickinson
  Denker (Berkeley), Vivek De (Georgia Tech),
  Younis Knight (MIT), Moon Jeong (National
  Uni., Seoul), Kim Papaefthymiou (Ann Arbor)
  etc.
• Recent Kim Papaefthymiou (Ann Arbor), Roy
  (Purdue), Michael Frank (FSU), Amirante (Tech.
  Uni. of Munich), Wang, Liu, Xiao Huang (Ningbo
  Uni., China), Salama (UoT)
• Areas of Research Physics of Computing,
  Prospective Applications, Circuit Design, System
  Design, Clock-supply generation

Presented by Joydip Das - Oct. 21, 2005
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Adiabatic Circuits

• Is it Worthy despite
• The constraints Complex design procedure, extra
  overhead, slow operation, requirements for new
  manufacturing procedures
• Yes, because
• In some cases (e.g., in sensor network,
  applications of handheld devices etc.), we are
  more concerned about energy rather than speed.
• Also, it is becoming increasingly difficult to
  control the heat, generated due to the
  irreversible computing by ever-increasing no. of
  gates and switching of conventional circuits.
• This technique can reduce power without scaling
  down voltage and thus may help addressing the
  leakage power issue etc...

Presented by Joydip Das - Oct. 21, 2005
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Adiabatic Circuits

• Basics of Adiabatic Circuits
• Conventional CMOS

When PFET is Switched ON, Energy from
SourceCV2 Energy in Capacitor ½CV2 Energy Lost
½CV2 -gt PFET
When NFET is Switched, Energy Drained ½CV2
Energy Lost ½CV2 -gt NFET
A switching event always dissipates energy equal
to signal energy, ½CV2
Presented by Joydip Das - Oct. 21, 2005
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Adiabatic Circuits

• Basics of Adiabatic Circuits
• Adiabatic Charging (Koller Athas, 1992)

Q CV I Q/T CV / T Ed I2RT (CV/T)2RT
(2RC/T) (½CV2) (2RC/T) Signal Energy
Compare with thermodynamic adiabatic principle
Very slow changes dissipate less energy. For
infinitely slow changes, total dissipation will
be zero, resulting in Brownian Computers
Presented by Joydip Das - Oct. 21, 2005
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Adiabatic Circuits

• Basics of Adiabatic Circuits
• Adiabatic Switching Koller Athas, 1992

• Three-valued logic used True, False,
  de-Energized
• When the output is de-Energized, the inputs can
  be changed with dissipation of energy
• The inputs are changed to a stable value
• Output states are changed by ramping up the
  supply voltage
• Outputs are changed and get stable
• Once stable, outputs can be used for the next
  stage

Presented by Joydip Das - Oct. 21, 2005
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Adiabatic Circuits

• Basics of Adiabatic Circuits
• Adiabatic Switching - Example Koller Athas,
  1992

• X, Ys get stable
• S2 and S1 are closed
• Charge flows to Z or Z
• When Z or Z is fully charged, S2 is opened
• Z or Z now maintains

• states and can be used in following stages
• To discharge, S2 is closed again
• RC/T is controlled by controlling T through L

Presented by Joydip Das - Oct. 21, 2005
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Adiabatic Circuits

• Basics of Adiabatic Circuits
• Adiabatic Latch and Inevitable Energy Loss
  Koller Athas, 1992

• Z, Z are charged S, S are opened. Z, Z
  maintain states through PFETs

• During de-Energizing, charge flows from output to
  supply adiabatically and dissipates energy ? 1/T
  until output gets down to Vth. The remaining
  energy ½CVth2 is lost as heat
• ½ CVth2 is the irreducible energy loss and can
  not be recovered
• We can not break kT barrier (kT can not be bigger
  than switch sensitivity, ½CgVth2, due to thermal
  noise)

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Adiabatic Circuits

• Basics of Adiabatic Circuits
• Characteristics of Adiabatic CMOS Circuits
  Koller Athas, 92

• The energy dissipation of combinational logic can
  be made arbitrarily small
• Information loading into memory circuits consume
  small amount of energy
• Erasing last copy of a piece of information
  inevitably dissipates an irreducible finite
  amount of energy

Presented by Joydip Das - Oct. 21, 2005
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Adiabatic Circuits

• Basics of Adiabatic Circuits
• Power Supply of Adiabatic CMOS Circuits

• Inputs of one stage needs to be stable before
  they are applied
• While inputs are asserted, the supply is in
  evaluation mode
• Outputs of one stage needs to be stable while
  evaluated by the next stage
• Energy is recovered during the ramp-down of the
  power supply.
• While output is de-energized, the power supply is
  idle

Presented by Joydip Das - Oct. 21, 2005
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Adiabatic Circuits

• Basics of Adiabatic Circuits
• Power Supply of Adiabatic CMOS Circuits

Presented by Joydip Das - Oct. 21, 2005
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Adiabatic Circuits

• Some of the Proposed Adiabatic Circuits
• Based on Power Supply Consequent Evaluation

• 2N-2N2D, 2N-2P, ECRL (Efficient Charge Rec.
  Logic), PAL (Pass-Transistor Adia. Logic), TSEL
  (True Single Phase Adia. Logic), QSERL
  (Quasi-Static Energy Recovery Logic) etc.
• All the earlier designs applied multi-phase
  trapezoidal power supplies. Some of them use six-
  or more phases. Some used diodes to maintain
  reversibility
• Some of the recent proposals use sinusoidal
  waves characteristics instead of multi-phase
  trapezoidal waves

Presented by Joydip Das - Oct. 21, 2005
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Adiabatic Circuits

• Some of the Proposed Adiabatic Circuits
• Inverters ECRL (Moon Jeong, 1996)

Circuit No Diode
Outputs Energy is oscillating and increases with
time
Chains
Presented by Joydip Das - Oct. 21, 2005
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Adiabatic Circuits

• Some of the Proposed Adiabatic Circuits
• Inverters ECRL (Moon Jeong, 1996)

Energy Comparison
Presented by Joydip Das - Oct. 21, 2005
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Adiabatic Circuits

• Some of the Proposed Adiabatic Circuits
• Positive Feedback Adiabatic Logic (Amirante et.
  al., 2003)

General Schematic Cross-coupled transistors
form the adiabatic block Only NMOS used for
combinational blocks F and F' blocks are
realized by static design
Presented by Joydip Das - Oct. 21, 2005
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Adiabatic Circuits

• Some of the Proposed Adiabatic Circuits
• Positive Feedback Adiabatic Logic (Amirante et.
  al., 2003)

1-Bit Full-Adder Circuit Energy Diagram
Presented by Joydip Das - Oct. 21, 2005
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Adiabatic Circuits
Some of the Proposed Adiabatic Circuits QSERL
(Yiben Ye Roy, 1997, 2001, (?)2005)

• Sinusoidal supply used
• Easily convertible from static
• Eval. Four Cases possible
• X-Low pMOS-ON X follows supply phi to HIGH
• X-Low nMOS-ON X remains low-gtno transition
• X-High pMOS-ON X remains high-gtno transition
• X-High nMOS-ON X follows phi to LOW

Presented by Joydip Das - Oct. 21, 2005
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Adiabatic Circuits
Some of the Proposed Adiabatic Circuits QSERL 8
X 8 Multiplier

• Organization was identical with CMOS carry-save
  multiplier
• Multiplier was simulated using MOSIS 0.5 µm CMOS
  n-well process
• Compared with static CMOS with same transistor
  sizing

Observations High clock frequency reduces energy
savings. The diode sizing increases and
consequently RC/T dissipation increases Throughpu
t is reasonable. Latency is large twelve clock
phases
Presented by Joydip Das - Oct. 21, 2005
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Adiabatic Circuits
Some of the Proposed Adiabatic Circuits TSEL
(Kim Papaefthymiou, 2001, 2005)
Presented by Joydip Das - Oct. 21, 2005
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Adiabatic Circuits
Clock Generation Circuits
Clockwise QSERL, Four-Phase, True-Single Phase
Observations LC tank oscillator is used to
generate power supplies (clock) for adiabatic
circuits
Presented by Joydip Das - Oct. 21, 2005
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Adiabatic Circuits
My Works

• Testing the existing techniques in 0.13µm
  technology
• Effect due to low voltage swing available
  (0.3-1.2)
• Ramping up between these voltage swings
• Capacitances that become prominent
• Estimation of the leakage power of the existing
  techniques - WIP
• Design of clock generation circuits
• Design of adder circuit using adiabatic technique

Presented by Joydip Das - Oct. 21, 2005
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Adiabatic Circuits
My Works Simulation ECRL Circuit
Presented by Joydip Das - Oct. 21, 2005
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Adiabatic Circuits
My Works Simulation ECRL Clock Power
Presented by Joydip Das - Oct. 21, 2005
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Adiabatic Circuits
My Works Simulation PFAL Circuit (Amirante
et. al., 03)
Presented by Joydip Das - Oct. 21, 2005
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Adiabatic Circuits
My Works PFAL Waves
Presented by Joydip Das - Oct. 21, 2005
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Adiabatic Circuits
My Works PFAL Power
Presented by Joydip Das - Oct. 21, 2005
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Questions ? Thank You