|Dimensions||2500μm x 2500μm|
This ASIC is a monophonic MIDI synthesizer with 16bit digital stereo sound output, sampled at 44.1kHz. The waveform is generated using 8 sine or rectangle oscillators representing the fundamental frequency and the first seven harmonics. Additional components such as an opto coupler at the input and a digital-to-analog converter (DAC) at the output are needed for operation. To allow for various types of DACs, two formats of digital output are implemented: the widely used I2S-format and a format for DACs requiring a latch enable signal.
Apart from receiving the notes it has to play, the chip also receives all configuration information over the serial MIDI interface. Configuration options are for example the amplitude envelope of each of the eight oscillators defined by attack time, decay time, sustain level, and release time (ADSR). Rectangle or sine output, volume, and location in the stereo panorama of each oscillator can also be controlled. A software with graphical user interface to play sounds and configure the chip was developed and tested.
The ASIC has been fabricated in a 0.25um five metal layer CMOS process. About two thirds of the fixed die size (2.5mmx2.5mm) are used by the circuit. Therefore only a few signals had to be routed on metal five as can be observed on the chip micrograph.