ams AS5900 CT 检测器接口

AS5851B是一款16位、256通道低噪声电荷-数字转换器，专为数字X射线系统设计。具有高度可编程性，能够在各种应用中实现系统性能优化。快速、低噪声和低功耗的组合最大限度地提高了图像质量，最大限度地减少了患者剂量和暴露，同时缩短了产品上市时间。每个通道前端包括一个电荷灵敏放大器（CSA）和一个相关双采样器（CDS），可消除信号中的偏置和闪烁噪声，并将其转换为数字信号。快速可靠的LVDS接口可在芯片外传输输出数字数据。内置的诊断功能可定位从检测器到数据采集系统的信号链中的错误源。芯片上还包括电压参考和温度传感器。通过SPI接口可轻松对器件参数进行编程。两种不同的电源模式可让用户在所选速度下将功耗降至最低。线扫描时间为40和80 μs时，每个通道的功耗分别仅需1.6和1.1 mW。此外，还可以将相邻通道中的电荷相加；通过这种分档，可实现的最快线扫描时间为20 μs。

The AS5912 is an ultra-low noise, 512-channel low power current to digital converter that enables the readout of photodiodes of a CT detector with highest sensitivity. The output currents of 512 photodiodes are converted simultaneously into digital without any dead time resulting in no charge loss on the inputs. The AS5912 combines current-to-voltage integration and A/D conversion for 512-channels in one device. The ADC architecture with its low-noise integrators, coarse quantizer, sample-and-hold and fine quantizer guarantee lowest input related noise of maximum 0.29 fC (low noise mode) at an input current range of 0.5 µA. The input current range of the ADC is selectable between 0.5 µA and 1 µA.The AS5912 supports two supply concepts: a single analog and true ground supply, in both modes the photodiodes are zero biased for ultra-low dark current of the photodiode. In true ground mode, the AS5912 operates at ±1.5 V dual analog supply while in single supply mode only a single analog supply of +3.0 V is needed. The device detects automatically the chosen supply concept. No external components are required for supply decoupling. To reduce PCB area and simplify the assembly process, decoupling capacitors for supply and reference voltages are integrated in the 23 x 15 mm² FBGA package. The on-chip LDOs, reference voltages and a temperature sensor minimize the external component requirements and reduces the bill of material.Full-scale range, integration time and power mode are configurable over a SPI-compatible serial interface as well as the digital output modes of the LVDS interface. In low power mode, the power dissipation can be minimized down to 1.25 mW per channel for reduced self-heating of the CT detector. The adjustable integration time down to 51 µs allow very high frame rates.