AS5950 Module Reference Design
The reference design is an example of a 16-slice CT detector module, featuring the AS5950 CT detector sensor chip. The AS5950 combines ADC and photodiodes side-by-side on a single CMOS chip. Therefor there is no need of assembling ADCs on the bottom side of the board. This two-side buttable module reference design has 2x2 pcs of AS5950 assembled on one substrate to build a sensor area of 32 x 16 mm². The sensor is directly assembled using a wire bonding process for manufacturing of a cost optimized CT module. It features a single standard flex connector on the bottom side to connect the board to an FPGA.
AS5950 CT Sensor Chip
The total sensor dimension in Z-direction is selectable between 16 or 32 mm, enabling two modes of operation. The adaptive array concept allows either a high resolution or a large sensor size on the detector. Pixel dimensions can be customized on request. The available standard product comes with a pixel dimension of 0.98x0.98 mm². The sensor can be directly assembled on a substrate using a wire bonding process for manufacturing of a CT module.
Superior image quality can be achieved because the input-related noise is very low. In high-resolution mode a typical noise of 0.20 fC can be reached including the photodiode. This ultra-low noise figure is the result of the small capacitance of the photodiode, and the very low parasitic capacitance of the interconnect between the photodiode and its corresponding ADC channel.
The low power consumption of typ. 0.65 mW per channel reduces self-heating effects and reduces the overall cost of cooling the system. The digital data readout can be accessed via SPI interface. It is also used to configure parameters such as pixel resolution, input current range, active sensor area and enabling the calibration mode. An integrated temperature sensor enables monitoring of the junction temperature. Featuring on-chip photodiodes, the AS5950 offers a cost-optimized solution and is delivered as die on foil.