Current-to-digital converters for CT scanners with ultra-low noise, high resolution and superior linearity

Ams AG, the world's leading provider of high-performance sensor solutions, announced the AS5900, a current-to-digital converter for CT scanners that delivers ultra-low noise, high resolution and superior linearity. The AS5900's excellent analog performance will enable the new CT scanner to deliver sharper, more detailed images. Medical CT scanners equipped with the AS5900 will have an improved X-ray detector module that will help doctors make more accurate diagnoses while giving patients lower radiation levels.

The AS5900 detector interface chip for CT X-ray scanners sets new standards for key parameters of the device:

● Low noise: only 3,200 electrons at full scale operation with 1µA input current and 30 pF input capacitance. The circuit's high signal-to-noise ratio allows flexible use of any pixel size, enabling it to digitize ultra-low current outputs in the latest high-sensitivity photodiodes. As a result, CT scanners can provide more detailed and richer pictures. In addition, low noise allows CT equipment to reduce the amount of X-ray radiation the patient receives while maintaining high resolution.

● Very low power consumption: Power consumption as low as 1mW per channel reduces the CT scanner's need for cooling capacity and reduces overall system costs.

● High resolution: The AS5900's integrated 26-bit analog to digital converter enables a richer gray-scale color palette, resulting in sharper, more detailed pictures.

●  High linearity: Read out ±250 ppm(full scale error ±1 ppm) provides improved contrast and accurately represents slight changes in image brightness.

Ams' new detector chip provides detailed motion-free medical images and operates at a high acquisition rate: adjustable integration times can be set as low as 50µs.

The AS5900's configurable design gives it the flexibility to integrate with different end devices, which typically use a single multi-channel photodiode array. The chip is ideal not only for medical devices, but also for industrial and security CT scanners. The device designer can configure or adjust it:

● Gain setting, full scale input current and background noise configuration

● Power mode, ADAPTS to the power consumption required by the detector

● Clock frequency, balanced resolution according to the required integration time

The AS5900 integrates all the functions of a current input ADC to minimize the need for external components. It includes an internal reference voltage and temperature sensor. This reduces the bill of materials, thereby reducing system costs. The AS5900 also provides a standard LVDS interface to the host FPGA(field Programmable Gate Array), running at data rates of up to 80 Mb/s for optimized power consumption.

Josef Pertl, Product Market Manager, AMS Semiconductor, said: "The AS5900's ultra-low noise and high resolution will enable CT scanner Oems to achieve better imaging results at higher full scale ranges, with the flexibility to control pixel sizes. Based on this new, high-performance current-to-digital converter, healthcare professionals will be able to see a significant difference in image quality and clarity in the next generation of CT scanners. The device's low noise characteristics at high speed and low power operation will result in CT images without motion artifacts, even at low radiation amounts and the highest rotational speeds."