Logic Design for Array-Based Circuits

by Donnamaie E. White

Copyright © 1996, 2001, 2002 Donnamaie E. White


Power Considerations

Last Edit July 22, 2001

Power Reduction Techniques

Regardless of the array technology, items whose use will increase the power dissipated by the array should be carefully chosen. A tradeoff or balance of different design objectives should reflect judicious selections that maintain speed while keeping power dissipation to a minimum and circuit size within the array constraints. Power considerations are no less serious for the large CMOS and BiCMOS arrays.

Table 7-8 summarizes the design choices that contribute to higher power; which choices are possible depends on the array series.

Table 7-8 Power Dissipation Contributors

Contributors to Power Dissipation
  • High-speed macro options
      propagation delay - faster
  • High fan-out macro options
      low distortion
      propagation delay - may be faster
  • Driver macros (clock drivers)
      low distortion
      propagation delay - may be faster
  • Multi-cell macros
      lower cell count
      propagation delay - may be faster
  • Unused outputs
      -no contribution-
  • Powered-down unused outputs
      -no contribution-
  • Unused inputs
      -no contribution-

Table 7-9 summarizes the choices that can be made to reduce power and the design tradeoffs that these may require.

Table 7-9 Low Power Options

Low Power Dissipation Tradeoff
Low-power macro options higher propagation delay
distortionless drive (maybe)
higher distortion drive (maybe)
Placement of I/O to reduce bias
or overhead current
less flexibility in placement;
less performance (maybe)



Copyright @ 2001, 2002 Donnamaie E. White, White Enterprises
For problems or questions on these pages, contact dew@Donnamaie.com