A Resonant Clock Generator for Single-Phase Adiabatic Systems

A Resonant Clock Generator for Single-Phase Adiabatic Systems Conrad H. Ziesler Marios C. Papaefthymiou University of Michigan, Ann Arbor, MI Suhwan Kim IBM, T.J. Watson Research Center, Yorktown Heights, NY Advanced Computer Architecture Laboratory Department of Electrical Engineering and Computer Science University of Michigan, Ann Arbor, MI

Motivation • Practical single-phase charge-recovery chip @ 200MHz • Efficient and simple integrated clock generator Clock Generator

Efficiency 207 MHz Reactive efficiency % Component tolerance %

Single Phase Charge Recovery • Time-varying “Power-Clock” U(t) • Recover charge from load C • Distribute charge transfer through transistors R over available time How to efficiently generate U(t) ?

C1 V1 S1 L R V2 S2 C2 Resonant Clock Generation • Power Switches: S1, S2 • External DC Supplies: V1, V2 • External/Bondwire Inductor: L • Adiabatic Load Model: R, C1, C2

C1 V1 S1 L R V2 S2 C2 Resonant Currents • Arrows show primary charge and discharge currents. • Switches do not conduct primary currents. • Switches can therefore be relatively small and efficient.

Switch Timings • Inductor current builds linearly when switches are on. • Peak switch current less than peak inductor current. • Switch S1 turned on at positive voltage peak. • Switch S2 turned on at negative voltage peak. Inductor current Output voltage

Control Logic gp i gn Ring Oscillator Pulse Generator Gate Driver • Asynchronous State Machine: • Alternates pulses to switches • Preserves pulse widths • Halves frequency gp gn

Tuning Frequency and duty cycle contours

Implementation Ring Osc Pulse Gen Gate Drive 25 tr. 19 tr. 10 tr. Power Switches: S1, S2 • 0.5 um CMOS N-Well Process • 60 pF Adiabatic Load @ 140 MHz • Compact: 170 x 115 um • External ~10 nH Inductor Power Clock

Waveforms Vdd Power-Clock 140MHz Vss

Conclusion • Resonant LC based clock generator • Reactive efficiencies over 90% @ 200 MHz • Compact design, 0.019 mm^2 • Scalable to large capacitive loads • Fabricated in a 0.5 um standard CMOS process • Tested with real adiabatic circuit, ~60 pF @ 140 MHz

Acknowledgments This research was supported in part by the US Army Research Office under ASSERT Grant No. DAAG55-97-1-0250 and Grant No. DAAD19-99-1-0304 Fabrication performed by: MOSIS Integrated Circuit Prototyping Service Advanced Computer Architecture Laboratory Department of Electrical Engineering and Computer Science University of Michigan, Ann Arbor, MI

For Additional Information www.eecs.umich.edu/acal/adiabatic Conrad Ziesler, cziesler@eecs.umich.edu Suhwan Kim, suhwan@us.ibm.com Marios Papaefthymiou, marios@eecs.umich.edu A Single-Phase Resonant Clock Generator ISLPED, Aug. 2001 Design, Test, and Measurement of a True Single-Phase Adiabatic Multiplier ARVLSI, March 2001 A True Single-Phase 8-bit Adiabatic Multiplier DAC, June 2001 True Single-Phase Adiabatic Circuitry IEEE Trans. VLSI, Feb. 2001

A Resonant Clock Generator for Single-Phase Adiabatic Systems