Universal USB audio back-end (9903)

Hanover, March 18, 1999 - At CeBIT '99, MICRONAS INTERMETALL, one of the foremost manufacturers of mixed-signal ICs, presents the first member of its new USB audio controller family, the UAC 3552A.

The UAC 3552A is a programmable USB DAC which supports different data rates and audio formats and, in addition to carrying out the digital-to-analog conversion, also performs the baseband processing of the audio signals. This means that a powerful and universal single-chip audio back-end is now available to all manufacturers of PC components which, among other applications, can be used in active loudspeakers, headphones, or interfaces to consumer electronics equipment.

The universal periphery bus

USB is short for Universal Serial Bus and stands for a standard serial PC peripheral interface which is currently establishing itself as the de-facto standard in the PC world. Not only a keyboard and a mouse, but also a joystick, speakers, headphones, digital camera, scanner, and PC telephone, for example, can be connected to the USB with no additional hardware or software and with the computer running ("hot plug-in"). The possible standard configurations of peripheral equipment are already taken care of in the bus protocol.

The USB provides a number of benefits for audio applications. First, there is no need for a sound card and its configuration. Second, the audio signals are transmitted digitally (and therefore noisefree) to the periphery where digital-to-analog conversion takes place. What is more, the control of baseband processing is integrated in the bus protocol.

The UAC 3552A from MICRONAS INTERMETALL fully supports the USB specifications 1.0 and 1.1; in particular, it is designed for the high data transfer rate of 12 MB/s as defined in the USB protocol. The IC processes 8, 16, and 24-bit audio data (mono or stereo) as well as input data rates of 5 to 48 kHz. The D-A converted signals are available in CD quality (96 dB signal/noise ratio, 0.01 % harmonic distortion) via two outputs. Output amplifiers for stereo headphones and operation amplifiers for external analog filters are integrated. Additional analog audio sources can be mixed into the converted signals via an analog input. This feature also ensures that the peripheral equipment concerned can be used for non-USB sources, too.

EEPROM and DSP integrated

Manufacturer and product data, for example a manufacturer and product identification code as well as product matching and operating parameters, can be stored in an integrated EEPROM. In this way, for example, 4 keys and 4 LEDs can be activated via the USB standard interface HID (Human Interface Device).

A digital signal processor (DSP) is also integrated. It is responsible for the sample rate conversion and the baseband processing; apart from audio baseband control (volume, bass/treble etc.), the 48 MHz DSP provides sufficient computing power to realize manufacturer-specific options. A particularly interesting feature here is the digital correction of the frequency response enabling the UAC 3552A to be matched to different products, for example loudspeakers of different quality. The corresponding programming of the EEPROM takes place directly via the USB and can be automated, i.e. carried out during final testing of the equipment.

Standard delivery and available package types

The UAC 3552A is supplied with a preprogrammed EEPROM in the 44-pin QFP package; test samples will be available in the second quarter of 1999. The standard delivery also includes a Windows 98-based programming software package.

Further products in the USB family from MICRONAS INTERMETALL, for example a USB codec, are in the development pipeline.