Adiabatic Switching. A Survey of Reversible Computation Circuits. Benjamin Bobich, 2004

Transcription

1 Adiabatic Switching A Survey of Reversible Computation Circuits Benjamin Bobich, 2004

2 Agenda for Today 1. The Basics of Adiabatic Logic and the Fundamentals of Adiabatic Charging 2. Early Adiabatic Circuit Structures 3. Modern Adiabatic Logic Families 4. Difficulties and Remedies for Adiabatic Circuits 5. Final Remarks

3 Agenda for Today The Basics of Adiabatic Logic and the Fundamentals of Adiabatic Charging Early Adiabatic Circuit Structures Modern Adiabatic Logic Families Difficulties and Remedies for Adiabatic Circuits Final Remarks

4 Basics of Adiabatic Logic Adiabatic: occurring without loss or gain of heat Conventional CMOS Changing value of bit requires converting bit signal into heat 2 States: True, False Speed is outstanding, but power dissipation is now a huge issue. Adiabatic CMOS Returns value (energy) of the bit back to the source 3 States: True, False, Off Very low power dissipation is achieved at expense of speed.

5 Theory of Reversible Computation The energy dissipation ( E) of combinational logic can be made arbitrarily small by operating the circuit slowly enough [1]. Q: What s arbitrarily small, and what is slow?

6 Power Dissipation in Adiabatic Charging On resistance Q=CV I=Q/T=CV/T E=I 2 RT (Resistor) =(CV/T) 2 RT =(2RC/T)(1/2 CV 2 ) Charging a load capacitance through a switch Better than CMOS by a factor of (2RC/T) [2]

7 Agenda for Today The Basics of Adiabatic Logic and the Fundamentals of Adiabatic Charging Early Adiabatic Circuit Structures Modern Adiabatic Logic Families Difficulties and Remedies for Adiabatic Circuits Final Remarks

8 Early Adiabatic Circuit Structures [2] Power Supply Adiabatic AND

9 Early Adiabatic Latch [2] (Latch) Adiabatic Switching, Low Energy Computing, and the Physics of Storing and Erasing Information J. G. Koller W. C. Athas 1993

10 Agenda for Today The Basics of Adiabatic Logic and the Fundamentals of Adiabatic Charging Early Adiabatic Circuit Structures Modern Adiabatic Logic Families Difficulties and Remedies for Adiabatic Circuits Final Remarks

11 To Modern Adiabatic Logic Circuits Original circuits were good conceptual models, but not very practical practical circuits. Hot Clock NMOS was published in 1985 by Charles Seitz at Cal-Tech [3]. It included the idea of a power-clock, but involved no charge recovery circuit. In 1993, Adiabatic Switching, Low Energy Computing, and the Physics of Storing and Erasing Information was published by William Athas and Jeff Koller. (Previous slides came from it) CMOS paper entitled Low-Power Digital Systems Based on Adiabatic Switching Principles, was published by Athas in Dec. of 1994 [4]

12 Modern Adiabatic Logic Families In June 1994 John Denker came up with the 2N-2N2D adiabatic logic family and 2N-2N2P Logic 1 year later (Shown Right). 2N-2N2P Adiabatic AND [5]

13 Modern Adiabatic Logic Families Pass Trans. Adiabatic Logic (PAL) [6] *Different from CPERL, mentioned later Clocked CMOS Adiabatic Logic (CAL) [7]

14 Modern Adiabatic Logic Families Complementary Pass Transistor Energy Recovery Logic Inverter (CPERL) [8] Adiabatic Pseudo-Domino Logic Inverter (APDL) [9] Diodes are a problem

15 Modern Adiabatic Logic Families True Single Phase Energy Recovering Logic (TSEL) [10] PMOS NMOS Paved the way for SCAL and SCAL-D

16 TSEL Timing Waveform [10]

17 Most Promising Logic Families Source Coupled Adiabatic Logic with Diode Connected X s (SCAL-D) [11] First adiabatic technology designed specifically for high speed. Positive Feedback Adiabatic Logic (PFAL) [12] Best flip-flop based adiabatic solution as far as power and drivability are concerned. Recent research suggests that SCAL-D and PFAL are the most practical by today s standards. [11,13]

18 Basic PFAL Adder, Inverter, and Timing [14]

19 SCAL-D Buffers (Enhancement of TSEL) [15] PMOS Buffer NMOS Buffer

20 Cascaded PNPN in SCAL-D [15] P N P N

21 Agenda for Today The Basics of Adiabatic Logic and the Fundamentals of Adiabatic Charging Early Adiabatic Circuit Structures Modern Adiabatic Logic Families Difficulties and Remedies for Adiabatic Circuits Final Remarks

22 Challenges of Recovery Circuits There are two big challenges of energy recovering circuits: 1. Circuit implementation of time-varying power sources 2. Computations should be implemented by low overhead circuit structures that use standard MOSFET devices

23 Synchronous Resonant Power Clock Generator [16]

24 Problems of Adiabatic Logic It is very slow by today s standards. It requires 50% more area than conventional CMOS, and simple circuit designs can be very complicated (consider previous slides. However: A multiplier built by Marios Papaefthymiou at the University of Michigan operated at 200 MHz at.25 the power dissipation of conventional CMOS (2003) [15] A.13um 8 Bit Ripple Carry Adder was constructed at Infineon. Significant Energy savings were only acheivable below 100 MHz, with 6x less energy dissipation than CMOS at 20 MHz (2003) [14]

25 Fixing the Speed Problem Adiabatic circuits face difficulties in speed for a number Of reasons: Charging time is inherently much slower than CMOS Adiabatic circuits are difficult to pipeline. Increasing speed of adiabatic circuits enlarges power-clock data sensitivity Factors at work aiding the speed problem: Scaling decreases R and C, which naturally makes T smaller Multiple power-clock designs to handle pipelining New Technoligies (like SCAL) that use only X s to eliminate DC lines. SCAL is the first real speed oriented adiabatic technology.

26 Agenda for Today The Basics of Adiabatic Logic and the Fundamentals of Adiabatic Charging Early Adiabatic Circuit Structures Modern Adiabatic Logic Families Difficulties and Remedies for Adiabatic Circuits Final Remarks

27 Final Remarks Adiabatic circuitry will always be behind conventional CMOS in speed, but as conventional CMOS gets faster Adiabatic circuitry will get faster as well. It may become practical in the near future. Source Coupled Adiabatic Logic is the most promising technology at this time. Single phase clocking is less complicated to implement, but multiple phase clocking is faster. Which will win? If Source Coupled Adiabatic Logic prevails, great attention must go into sinusoidal clock generator circuits.

28 References [1] Landauer, Rolf Irreversibility and Heat Generation in the Computing Process, IBM Journal, July 1961, pp [2] Koller, J. G., Athas, W. C. Adiabatic Switching, Low Energy Computing, and the Physics of Storing and Erasing Information, Proceedings of the Workshop on Physics and Computation, PhysComp 92, Dallas, Texas, Oct. 2-4, 1992 IEEE Press, 1993, pp [3] Seitz, C., Hot Clock nmos, Proceedings of the 1985 Chapel Hill Conference on VLSI, Computer Science Press, 1985 [4] Athas, W.C. et.al, Low-Power Digital Systems Based on Adiabatic Switching Principles, IEEE Transactions on VLSI Systems, Dec pp [5] Denker, John S. A Review of Adiabatic Computing, 1994 IEEE Symposium on Low Power Electronics pp [6] Oklobdzija, Maksimovic, Lin, Pass-Transistor Adiabatic Logic Using Single Power Clock Supply IEEE Transactions on Circuits and Systems-II Analog and Digital Signal Processing, Vol. 44, No. 10, Oct pp [7] Maksimovic, Oklobdzija, Nikolic, Current, Clocked CMOS Adiabatic Logic with Integrated Single-Phase Power Clock Supply, Experimental Results, ACM, Inc. August 1997 pp

29 References [8] Chang, Hung, Wang, Complementary pass-transistor energy recovery logic for low-power Applications, IEE Proceedings March 2002 pp [9] Wong, H.H. Lau, K. T. Adiabatic Pseudo-Domino Logic with Dual Rail Inputs, 2001 pp [10] Kim S. and Papaefthymiou M.C., True single-phase energy-recovering logic for low-power, high-speed VLSI, Proc. Int. Symp. Low-Power Electron. Design, Monterey, CA Aug pp [11] Kim, S. and Papaefthymiou, M. C. True Single-Phase Adiabatic Circuitry IEEE Transactions on VLSI Systems, Vol. 9 No. 1 February 2001 pp [12] Vetuli, A. Pascoli, S.D. Reyneri, L.M. Positive Feedback in Adiabatic Logic Electronics Letters, 26 th September 1996 Vol. 32 pp [13] A. Blotti, S. Di Pascoli, R. Saletti, A comparison of some circuit schemes for semi-reversible adiabatic logic, Int. J. Electronics, 2002, Vol. 89 pp [14] Schmitt-Landsiedel, Doris; Amirante, Ettore; Jurgen, Fischer; An Ultra Low- Power Adiabatic Adder Embedded in a Standard.13um CMOS Environment, April 2003 pp [15] Papaefthymiou, Ziesler, Kim, Design, Verification, and Test of a True Single- Phase 8-bit Adiabatic Multiplier, June 2001 pp [16] Mahmoodi-Meimand, Afzali-Kusha, Efficient Power Clock Generation For Adiabatic Logic, September 2001 pp

30 Questions?