IEEE Trans Biomed Circuits Syst. 2020 Apr;14(2):359-372. doi: 10.1109/TBCAS.2020.2973508. Epub 2020 Feb 12.
An ultra-high frame rate and high spatial resolution ion-sensing Lab-on-Chip platform using a 128 × 128 CMOS ISFET array is presented. Current mode operation is employed to facilitate high-speed operation, with the ISFET sensors biased in the triode region to provide a linear response. Sensing pixels include a reset switch to allow in-pixel calibration for non-idealities such as offset, trapped charge and drift by periodically resetting the floating gate of the ISFET sensor. Current mode row-parallel signal processing is applied throughout the readout pipeline including auto-zeroing circuits for the removal of fixed pattern noise. The 128 readout signals are multiplexed to eight high-sample-rate on-chip current mode ADCs followed by an off-chip PCIe-based readout system on a FPGA with a latency of 0.15 s. Designed in a 0.35 μm CMOS process, the complete system-on-chip occupies an area of 2.6 × 2.2 [Formula: see text] with a pixel size of 18 × 12.5 μ[Formula: see text] and the whole system achieves a frame rate of 3000 fps which is the highest reported in the literature for ISFET arrays. The platform is demonstrated in the application of real-time ion-imaging through the high-speed visualization of sodium hydroxide (NaOH) diffusion in water at 60 fps on screen in addition to slow-motion playback of ion-dynamics recorded at 3000 fps.
一种超高帧率和高空间分辨率的离子感应片上系统，使用 128×128 CMOS ISFET 阵列。采用电流模式操作以实现高速运行，ISFET 传感器偏置在三极管区域以提供线性响应。感应像素包括重置开关，允许通过周期性重置 ISFET 传感器的浮栅来进行像素内校准，以消除偏移、俘获电荷和漂移等非理想因素。电流模式行并行信号处理应用于整个读出流水线，包括自动归零电路，用于消除固定模式噪声。128 个读出信号被多路复用到八个高速采样率的片上电流模式 ADC，然后通过 FPGA 上的基于 PCIe 的读出系统进行处理，其延迟为 0.15s。该系统采用 0.35μm CMOS 工艺设计，整个片上系统占地面积为 2.6×2.2[公式：见正文]，像素尺寸为 18×12.5μ[公式：见正文]，整个系统实现了 3000fps 的帧率，这是文献中报道的 ISFET 阵列中的最高帧率。该平台在实时离子成像应用中得到了验证，通过在屏幕上以 60fps 的高速可视化氢氧化钠（NaOH）在水中的扩散，以及以 3000fps 的慢动作播放记录的离子动力学。
