Presentation is loading. Please wait.

Presentation is loading. Please wait.

Circuit Design Techniques for Low Power DSPs

Similar presentations


Presentation on theme: "Circuit Design Techniques for Low Power DSPs"— Presentation transcript:

1 Circuit Design Techniques for Low Power DSPs
Simone Gambini Marghoob Mohiyuddin Melinda Ler

2 Free Template from www.brainybetty.com
Motivation Energy Per Operation (EOP) important For energy-constrained systems, e.g., battery-powered devices Supply voltage scaling can be used to reduce energy consumption Leakage limits scaling to above a certain supply voltage Conventional techniques for low power/energy design may not be beneficial Low power designs also have performance constraints (apart from power) Design should meet throughput constraints while minimizing energy consumption Want to explore tradeoffs in design given these constraints 12/8/2018 Free Template from

3 Free Template from www.brainybetty.com
Problem Statement Study the impact of low power design techniques for different circuits with performance constraints Effects of process variations and temperature Supply voltage scaling Using parallelism to reduce power Architectural approaches Multiplier designs used as case studies Fundamental block in many DSP systems 12/8/2018 Free Template from

4 Free Template from www.brainybetty.com
Prior Work If energy per operation (EOP) used as an optimization metric then an optimal choice of Vdd exists [1] Technology, micro-architecture and architecture affect the EOP Minimum EOP point at EOP optimal Vdd shown to shift with different micro-architectures [2] Performance constraint not taken into account 12/8/2018 Free Template from

5 Free Template from www.brainybetty.com
Project Outline Technology characterization Simulated leakage and delay for 90nm technology node across process corners and temperature Modeling EOP Using simulated delay and leakage data for FO1 and FO4 ring oscillators Extrapolated to get predictions for EOP behavior for different micro-architectures Characterizing test circuits to validate our predictions Delay validation Power validation 12/8/2018 Free Template from

6 Technology Characterization: Process and Temperature Variation Effects
EOP Model Variations in EOP behavior for SVT and LVT across corners Variations of minimal EOP with temperature 12/8/2018 Free Template from

7 Technology Characterization: Process Options
Tradeoff exists between LVT and HVT process options for different operating frequencies with intermediate switching activities 12/8/2018 Free Template from

8 Parallelism and Pipelining
For constant throughput, pipelining allows for lower energy per operation at lower supply voltages Parallelism Due to overhead in hardware and increase in logic delay, parallel structures increases minimal energy per operation 12/8/2018 Free Template from

9 Case Study: Multipliers
Investigated multiple architectures Wallace tree multiplier Array multiplier Serial multiplier Impact of parallelism on EOP behavior Technology characterization predicts that parallelism increases EOP for low supply voltages Leakage becomes the dominating factor at low supply Higher leakage factor means optimal Vdd should increase with parallelism 12/8/2018 Free Template from

10 Flow for EOP estimation
Circuit synthesis (Module Compiler) Extraction of activity factor (ModelSim) Correlated input vectors generated with Matlab Gates annotated with activity factors and capacitances Delay simulation for critical paths (Spectre) Over multiple Vdds Power estimation (PowerPrime) Dynamic and leakage power for single supply voltage Power scaling with Vdd extrapolated using scaling factors from FO4 inverter chain 12/8/2018 Free Template from

11 Simulated EOPs for Multipliers
Parallelism yields energy benefits only above a certain Vdd Tradeoff between different architectures at different bitwidths Wallace tree is better than carry save for higher bitwidths Architectural decisions affect EOP strongly 12/8/2018 Free Template from

12 Free Template from www.brainybetty.com
Delay Validation Simulated critical path delays vs. extrapolated delays from inverter chain Delay scales proportionally to inverter delay 12/8/2018 Free Template from

13 Free Template from www.brainybetty.com
Leakage Validation Leakage power for the critical paths for a specific input vector Leakage power for a NAND4 gate with different input vectors A large variation in the leakage power over input vectors Total leakage power depends on the statistical distribution of input vectors over time Leakage does not scale the same way as inverter leakage 12/8/2018 Free Template from

14 Free Template from www.brainybetty.com
Leakage Validation Top figure shows leakage current for different input vectors Bottom figure shows leakage current for different input vectors weighted by the probability of the input vectors 12/8/2018 Free Template from

15 Free Template from www.brainybetty.com
Leakage Validation Sensitivity of the optimal Vdd point with respect to the leakage energy For sub-threshold operation, the optimal Vdd is not very sensitive to leakage energy [2] 12/8/2018 Free Template from

16 Conclusions & Future Work
For low power systems operating below a certain operating frequency, parallelism would not be the ideal option due to leakage This trend is expected to be reinforced in the future technology nodes Fast and accurate leakage estimation tools needed Should take into account the state-dependent behavior of leakage 12/8/2018 Free Template from

17 Free Template from www.brainybetty.com
References [1] D. Markovic, V. Stojanovic, B. Nikolic, M. A. Horowitz, and R. W. Brodersen, “Methods for True Energy-Performance Optimization,” IEEE Journal of Solid-State Circuits, vol. 39, pp. 1282–1293, Aug. 2004 [2] B. H. Calhoun and A. Chandrakasan, “Characterization and Modeling of Minimum Energy Per Operation Point,” in Proc. IEEE International Symposium on Low Power Electronics and Design, Newport Beach, California, Aug. 2004, pp. 90–95. [3] A. Wang and A. Chandrakasan, “A 180mV FFT Processor Using Subthreshold Circuit Techniques,” in Proc. IEEE International Solid-State Circuits Conference, Feb [4] Y. Taur and T. H. Ning, Fundamentals of Modern VLSI Devices. Cambridge University Press, 1999. 12/8/2018 Free Template from


Download ppt "Circuit Design Techniques for Low Power DSPs"

Similar presentations


Ads by Google