Electronic Design

Current-To-Digital Converter IC Improves CT Scanners’ Imaging

The ADAS1128 current-to-digital converter chip from Analog Devices enables high-slice-count computerized tomography (CT) systems to capture real-time moving images, such as a beating heart, with a high degree of accuracy and detail. This 24-bit device also changes photodiode-array signals into digital signals. It offers 128 data-conversion channels, provides an increase in speed from 6 to 20 ksamples/s, and supports four times more channels (128 versus 32) than any other integrated converter of its kind, according to the company. Thanks to the level of performance and integration, the ADAS1128 can mean a 50% reduction in the cost of a CT detection system’s electronics compared with older designs.

The chip replaces previous converter-based technology having low levels of channel integration. It integrates a 24-bit resolution analog-to-digital converter (ADC) with 128 simultaneously sampled data-converter channels, selectable sample rates up to 20 ksamples/s, and on-chip temperature sensor and reference buffer into a single 1-cm2 chip. In addition to supporting four times more channels, the product delivers over three times the throughput of any other comparable device, Analog Devices says.

The ADAS1128 consumes less than half the power of competing devices (4.5 mW/channel versus 10 mW/channel at full speed). It also offers superior overall performance specs, such as no charge loss, more choices of full scale ranges, and ultra-low noise (down to 0.4 fC for low-dose X-ray systems).

Available now in volume production, The ADAS1128 is housed in a compact 10- by 10-mm mini BGA (ball-grid array) package. Along with CT systems, the chip also enables the design of X-ray-based security imaging systems used in shipping yards, harbors, and airports.

Analog Devices


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