Analog/Mixed-Signal ICs: Digital-To-Analog Converters

Hybrid solutions will continue to take advantage of the fastest and greatest DAC chips on the market, combining them with the necessary functions and peripherals for a given application. In that way, they will deliver a complete high-performance solution from a single module.

Audio DACs with a 24-bit resolution and a 192-kHz sampling rate have achieved 120-dB SNR. AKM Semiconductor (www.akm.com) plans to integrate single-wire SPDIF interfaces on-chip to achieve performance at 3 V and below as well.

While the integration of analog and mixed-signal data converters with DSP processors or microcontrollers is common, merging a high-end DAC with a powerful DSP core on the same chip is a tough task. Analog Devices has recently made that integration possible (www.analog.com). ADI's SigmaDSP line integrates a 24-bit Δ-∑ DAC with a 25-MIPS DSP engine on the same piece of silicon. In fact, there are three such DACs with a 48-kHz sampling frequency on this chip. The signal-to-noise ratio is 112 dB. The built-in DSP executes algorithms for real-world limitations of speakers, amplifiers, and listening environments of perceived audio quality.

Employing its patented self-adaptive silicon technology, startup Impinj (www.impinj.com) is bridging the gap between precision analog and faster digital circuits using a leading-edge digital CMOS process. The company is developing a 14-bit DAC based on TSMC's 0.25-µm CMOS, with plans to migrate to 0.18-µm and finer CMOS geometries. Characterization is in progress. However, Impinj's 14-bit DAC boasts a spurious-free dynamic range of 80 dB at a sample rate of 250 Msamples/s, while consuming only 50 mW and occupying a die area of 0.17 mm². The goal is to provide two orders of magnitude improvement in linearity via self trimming and calibration techniques.

Six or more high-performance, multichannel DACs are now packed on a single CMOS chip to serve surroundsound applications requiring super-audio CD (SACD) playback or other multichannel audio systems like the DVD. For high-density data-acquisition applications, octals at 12 bits and quads at 16 bits with low power consumption are adequately serving designers' needs. Texas Instruments' Burr-Brown Division (www.ti.com) is looking to push such density to 40 channels per chip with very fast settling times.

Makers will continue to tap the integration density and low-power benefits of deep-submicron CMOS, while driving the update rate of 12-bit parts to a new high. Combining deep-submicron CMOS with a novel-segment shuffling technique in segmented current-steering architecture, Fujitsu Microelectronics (www.fujitsumicro.com) has dramatically boosted the update data rate for 12-bit DACs to 400 Msamples/s. Such high-resolution, high-speed DACs also come with on-chip interpolation filters. Signal Processing Technology (www.spt.com) is exploiting CMOS to create high-resolution, high-speed parts with unprecedented power consumption. Its 10-bit, 400-Mword/s DAC uses 0.25-µm CMOS to keep full-speed consumption at 130 mW. The supply voltage is 3 V. For low-speed 16-bit resolution, Texas Instruments' Burr-Brown Division (www.ti.com) has demonstrated maximum consumption of 2 mW at 5 V, which reduces to 1 µW in the power down mode.

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