A current-to-digital converter from Ams offers low noise, high resolution and linearity, enabling new CT scanners to produce sharper and more detailed images.

Medical CT scanners equipped with the AS5900 will gain an improved X-ray detector module that can help physicians to produce more accurate diagnoses while subjecting patients to lower doses of radiation.

The AS5900 detector interface chip allows as few as 3,200 electrons for a full-scale range at an input current of 1µA and 30pF input capacitance. The circuit’s very high signal-to-noise ratio allows the flexible use of any pixel size, enabling it to digitise extremely low-current outputs from the latest high-sensitivity photodiodes. As a result, the CT scanner can render more detailed images. Furthermore, low noise allows CT equipment to maintain high spatial resolution while reducing the X-ray dose to which the patient is exposed.

The AS5900 also offers power dissipation as low as 1mW per channel reduces the requirement for cooling capability in the CT scanner, while its integrated 26-bit sigma delta ADC produces a richer greyscale palette for sharper and more detailed images.

The AS5900 also features ±250ppm of Read inputs (±1ppm of full-scale range) to give improved contrast, accurately rendering slight variations in image brightness. It also provides detailed motion-free medical images while operating at very high acquisition rates: the adjustable integration time can be set as low as 50µs.

The configurable design of the AS5900 gives it the flexibility required for integration into different types of end equipment that use a multiple-slice photodiode array. The chip is ideal for use not only in medical equipment, but also in industrial and security CT scanners.

Ams_AS5900_block (cr) Figure 1: AS5900 block diagram. (Source: Ams)

The AS5900 is sampling in a 10mm x 10mm BGA package with unit pricing at $1/channel or $128 for the 128-channel AS5900 in 1,000-unit lots.