Electronic Design
20-Bit DAC Sharpens MRI Images

20-Bit DAC Sharpens MRI Images

Analog Devices developed its AD5791 (see the figure) high-accuracy 20-bit digital-to-analog converter (DAC) for magnetic resonance imaging (MRI) scanning devices. It’s equally useful in high-precision communications and instrumentation applications.

The DAC provides 1-ppm resolution and accuracy in a single device along with low noise (0.025 ppm low frequency, 9 nV√Hz wide-band) and output drift (less than 1 ppm), plus a 1-µs refresh rate. Offset drift is 0.05ppm/°C. Other specs include a guaranteed maximum ±1-LSB relative accuracy and guaranteed monotonic operation with ±1-LSB differential nonlinearity.

In MRI, other things being equal, higher DAC precision produces sharper image resolution. Analog Devices says the low noise, drift, and linearity of the AD5791 also increase operational up-time by eliminating the need to take the MRI system offline for system calibration cycles. The converter reduces the necessity for complex calibration algorithms, resulting in lower engineering and system maintenance costs as well. 

To help designers employ the AD5791, ADI provides an evaluation kit with PC software for real-time analysis, plus a reference design board with schematics, layout recommendations, and code. Further application support is available at [email protected].

Unit pricing is $38 for 1000-unit volumes. Packaging is a 24-pin thin-shrink small-outline package (TSSOP).

Analog Devices

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