Application specific integrated filters for HIFI digital audio signal processing

The semi-automatic design and integration of a digital audio preamplifier filter set is discussed. The set consists of an offset filter, 10 graphic equalizer sections and a scratch filter with an overall signal-to-noise ratio of 100 dB. A silicon compiler CATHEDRAL-I supports the design cycle from specifications to layout; the combination of synthesis with optimization tools at all design levels leads to a very compact silicon integration. An experimental chip integrates the offset filter, 3 equalizer sections and the scratch filter. The area is 24, 3mm²in coservative 6µm NMOS or 8mm²when scaling down to 3µm technology, allowing for functional densities up to 0.2 mm²/pole-zero. This demonstrates the potential for very cheap digital HIFI signal processing.