This paper addresses the design of asynchronous circuits for low power through an example: a filter bank for a digital hearing aid. The asynchronous design re-implements an existing synchronous circuit which is used in a commercial product. For comparison, both designs have been fabricated in the same 0.7-m CMOS technology. When processing typical data (less than 50-dB sound pressure), the asynchronous design consumes 85 W-a fivefold reduction compared to the synchronous design. This has been

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... hieved by the use of asynchronous control and data-path logic, an improved RAM design, and by a mechanism that adapts the number range to the actual need (exploiting the fact that typical audio signals are characterized by numerically small samples). Apart from the improved RAM design, these measures are only viable in an asynchronous design. The principles and techniques explained in this paper are of a general nature, and they apply to the design of asynchronous lowpower digital signal-processing circuits in a broader perspective. In fact, this understanding is one of the contributions of the paper. Finally, the paper can be read as an example-driven introduction to asynchronous low-power design.