Crystal Audio Codec

Crystal Audio Codec

The digital image presented above illustrates a minute portion of the surface of a Crystal Semiconductor CS4297 audio codec, termed the CrystalClear Sound Fusion Audio Codec '97 by the manufacturer. Included on the integrated circuit is a 20-bit stereo digital-to-analog converter, and 18-bit stereo analog-to-digital converter, four analog line-level stereo inputs, dual stereo line-level outputs, dual microphone inputs, and 3-D stereo enhancement. The chip was designed as a 2.1 compatible stereo audio codec designed for personal computer multimedia systems, and uses mixed signal technology to enable the design of desktop, portable, and entertainment computers. Intel and IBM were the primary manufacturers utilizing the chip, with over 10 million pieces being shipped to the companies.

During chip design meetings, the lead engineer, Mark Alexander, suggested as a joke that the designers fill in one of the empty spaces in a circuit row with a large switch to indicate that the chip was running. Designer Greg Rohde ran with the idea and created a double pole-double throw switch with a voltmeter below. Greg mentions that the switch and voltmeter are wired to the main analog power bus and the voltmeter is reading 5 volts.

  • View a higher magnification digital image of the double pole-double throw switch.

  • View a higher magnification digital image of the voltmeter.

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