A complete 18-bit audio D/A converter

A voltage-output digital-to-analog converter (DAC) for digital audio applications, which combines several conventional circuit architectures, is described. It uses high-resolution laser-trimming techniques to achieve total full-scale harmonic distortion plus noise of -94 dB, without external components or adjustments. The single-chip converter is integrated with an advanced high-density bipolar/CMOS process, resulting in a 6.2-mm/sup 2/ chip area, and is assembled in a 16-pin plastic package. The logic section includes TTL/CMOS translators for the three-input serial interface, an 18-b shift register, thermometer decoder for segmentation of the four MSBs, and an edge-triggered holding register for minimizing bit skew. The analog section consists of an 18-b binary-weighted current source DAC, bipolar offset circuitry, low-noise bandgap reference, and a low-distortion amplifier to provide voltage output. The core of the chip is a combination of three different DAC structures. The four most significant bits are segmented into 15 equally weighted current cells. Segmentation was chosen to decrease the component matching needed for good differential linearity and to decrease sensitivity to component drift over time, temperature, and packaging stress.<>