Readout Chip Research Articles

High-rate, high-resolution single photon X-ray imaging: Medipix4, a large 4-side buttable pixel readout chip with high granularity and spectroscopic capabilities

The Medipix4 chip is the latest member in the Medipix/Timepix family of hybrid pixel detector chips aimed at high-rate spectroscopic X-ray imaging using high-Z materials. It can be tiled on all 4 sides making it ideal for constructing large-area detectors with minimal dead area. The chip is designed to read out a sensor of 320 × 320 pixels with dimensions of 75 μm× 75 μm or 160 × 160 pixels with dimensions of 150 μm× 150 μm. The readout architecture features energy binning of the single photons, which includes charge sharing correction for hits with energy spread over adjacent pixels. This paper presents the specifications, architecture, and circuit implementation of the chip, along with the first electrical measurements.

Radiation Detector Front-End Readout Chip with Nonbinary Successive Approximation Register Analog-to-Digital Converter for Wearable Healthcare Monitoring Applications.

A 16-channel front-end readout chip for a radiation detector is designed for portable or wearable healthcare monitoring applications. The proposed chip reads the signal of the radiation detector and converts it into digital serial-out data by using a nonbinary successive approximation register (SAR) analog-to-digital converter (ADC) that has a 1-MS/s sampling rate and 10-b resolution. The minimum-to-maximum differential and integral nonlinearity are measured as -0.32 to 0.33 and -0.43 to 0.37 least significant bits, respectively. The signal-to-noise-and-distortion ratio and effective number of bits are 57.41 dB and 9.24 bits, respectively, for an input frequency of 500 kHz and a sampling rate of 1 MS/s. The SAR ADC has a 38.9-fJ/conversion step figure of merit at the sampling rate of 1 MS/s. The proposed chip can read input signals with peak currents ranging from 20 to 750 μA and convert the analog signal into a 10-bit serial-output digital signal. The input dynamic range is 2-75 pC. The resolution of the peak current is 208.3 nA. The chip, which has an area of 1.444 mm × 10.568 mm, is implemented using CMOS 0.18-μm 1P6M technology, and the power consumption of each channel is 19 mW. This design is suitable for wearable devices, especially biomedical devices.

Thermal and supply voltage analysis of optimized ring oscillator for pixel detector readout chip

This paper provides a specific study of the upgrade of the ATLAS pixel detector in preparation for the upgrade of the Large Hadron Collider (LHC). The upgrade to High Luminosity-LHC (HL-LHC) is expected to start after the long shutdown in 2025-2027. The scheduled upgrade for ATLAS will be able to efficiently cope with the challenges caused by the high luminosity imposed by the HL-LHC. A new full-silicon Detector Inner Tracker (ITk) will replace the current ATLAS Inner Detector (ID). The ITk pixel detector will consist of more layers than in the current pixel detector. This study focuses on the Ring Oscillator (ROSC) sensors embedded in the ITkPix-V1 Front-End chip of the ATLAS ITk pixel detector. The paper reports the frequency response of the ROSC at various temperatures and voltage supply values. The results showed a high sensitivity of ROSCs frequencies to the applied voltage and the external temperatures which indicates the reliability of the ITkPix-V1 chip for the future ITk pixel modules.

A Fingertip-Mimicking 12×16 200μm-Resolution e-skin Taxel Readout Chip with per-Taxel Spiking Readout and Embedded Receptive Field Processing.

This paper presents an electronic skin (e-skin) taxel array readout chip in 0.18μm CMOS technology, achieving the highest reported spatial resolution of 200μm, comparable to human fingertips. A key innovation is the integration on chip of a 12×16 polyvinylidene fluoride (PVDF)-based piezoelectric sensor array with per-taxel signal conditioning frontend and spiking readout combined with local embedded neuromorphic first-order processing through Complex Receptive Fields (CRFs). Experimental results show that Spiking Neural Network (SNN)-based classification of the chip's spatiotemporal spiking output for input tactile stimuli such as texture and flutter frequency achieves excellent accuracies up to 97.1% and 99.2%, respectively. SNN-based classification of the indentation period applied to the on-chip PVDF sensors achieved 95.5% classification accuracy, despite using only a small 256-neuron SNN classifier, a low equivalent spike encoding resolution of 3-5 bits, and a sub-Nyquist 2.2kevent/s population spiking rate, a state-of-the-art power consumption of 12.33nW per-taxel, and 75μW-5mW for the entire chip is obtained. Finally, a comparison of the texture classification accuracies between two on-chip spike encoder outputs shows that the proposed neuromorphic level-crossing sampling (NLCS) architecture with a decaying threshold outperforms the conventional bipolar level-crossing sampling (LCS) architecture with fixed threshold.

Serial powering characterisation for the CMS Inner Tracker at the High Luminosity LHC

The CMS tracking system will be completely replaced in order to operate in the extreme conditions of the High Luminosity LHC. The new tracker will consist of two main subdetectors: the Inner Tracker, containing pixel modules, and the Outer Tracker, consisting of strip and macro-pixel modules. In the Inner Tracker, silicon sensors will be read out by the CMS Readout Chip (CROC). The chip, built in 65 nm CMOS technology, is able to withstand high radiation doses (500 Mrad) and hit rates (3 GHz/cm2 on the innermost tracking layer) during operation. Moreover, it must handle a fine sensor granularity (2500 µm2 pixels) and operate at low detection thresholds (1000 e-). The Inner Tracker will make use of the serial powering scheme to provide the ∼60 kW required by ∼4000 modular units. The Shunt-LDO (SLDO) regulator is the part of the CROC responsible for providing the power by draining a constant current in time, independently of the chip power consumption. Tests performed with Single Chip Cards (SCC) in serial configurations are reported in this paper.

Advanced System-on-Chip Field-Programmable-Gate-Array-Powered Data Acquisition System for Pixel Detectors.

Particle detector systems require data acquisition systems (DAQs) as their back-end. This paper presents a new edge-computing DAQ that is capable of handling multiple pixel detectors simultaneously and was designed for particle-tracking experiments. The system was designed for the ROC4SENS readout chip, but its control logic can be adapted for other pixel detectors. The DAQ was based on a system-on-chip FPGA (SoC FPGA), which includes an embedded microprocessor running a fully functional Linux system. An application using a client-server architecture was developed to facilitate remote control and data visualization. The comprehensive DAQ is very compact, thus reducing the typical hardware load in particle tracking experiments, especially during the obligatory characterization of particle telescopes.

Plug-and-play smart transistor bio-chips implementing point-of-care diagnosis of AMI with modified CRISPR/Cas12a system

The point-of-care diagnosis of acute myocardial infarction (AMI), an extremely lethal disease with only a few hours of golden rescue time, is significant and urgently required. Here, we describe a plug-and-play carbon nanotube field effect transistor (CNT-FET) bio-chip supported with a smart portable readout for ultrasensitive and on-site testing of cardiac troponin I (cTnI), which is one of the most specific and valuable biomarkers of AMI. A modified clustered regularly interspaced short palindromic repeats (CRISPR)/Cas12a system, featuring the G-triplex structured reporter, was first combined with the CNT-FET to realize non-nucleic acid detection. Such a unique CNT-FET biosensor achieved the high sensitivity (LOD: 0.33 fg/mL), which is expected to give timely warning in the early stage of myocardial injury. In addition, a bilayer gate dielectric consisting of Y2O3/HfO2, employed into the passivation process, enabled the high environmental stability and repeatability of CNT-FET. More importantly, the homemade compact chip readout forged a field-deployable cTnI analytical tool, realizing “plasma-to-answer” performance for AMI patients in point-of-care testing scenarios. The developed technology holds promise to help doctors make clinical decisions faster, especially in remote areas.

Time calibration studies for the Timepix3 hybrid pixel detector in electron microscopy

Direct electron detection is currently revolutionizing many fields of electron microscopy due to its lower noise, its reduced point-spread function, and its increased quantum efficiency. More specifically to this work, Timepix3 is a hybrid-pixel direct electron detector capable of outputting temporal information of individual hits in its pixel array. Its architecture results in a data-driven detector, also called event-based, in which individual hits trigger the data off the chip for readout as fast as possible. The presence of a pixel threshold value results in an almost readout-noise-free detector while also defining the hit time of arrival and the time the signal stays over the pixel threshold. In this work, we have performed various experiments to calibrate and correct the Timepix3 temporal information, specifically in the context of electron microscopy. These include the energy calibration, and the time-walk and pixel delay corrections, reaching an average temporal resolution throughout the entire pixel matrix of 1.37±0.04ns. Additionally, we have also studied cosmic rays tracks to characterize the charge dynamics along the volume of the sensor layer, allowing us to estimate the limits of the detector’s temporal response depending on different bias voltages, sensor thickness, and the electron beam ionization volume. We have estimated the uncertainty due to the ionization volume ranging from about 0.8 ns for 60 keV electrons to 8.8 ns for 300 keV electrons.

Characterization results of the first small pixel high rate (SPHIRD) pixel detector prototypes

This work presents a summary of the experimental results and the performance obtained from a first set of p-type silicon SPHIRD prototypes. The SPHIRD project (Small Pixel High Rate photon counting Detector) targets a new generation of X-ray photon counting hybrid pixel detectors for synchrotron radiation applications, with small pixels and operating between 10 and 30 keV. The readout ASIC is designed to explore techniques that boost the count rate capabilities of the detector and methods to manage, or in some cases exploit, the effects of charge sharing that are unavoidable with small pixels in this type of detector.The achievement of high photon rates relies on the implementation of a fast charge-sensitive amplifier in the pixelin combination with pile-up compensation techniques, which have been compared experimentally. The obtained results show and quantify their effectiveness in increasing the count-rate handled by the detector.The readout chip also includes dedicated circuitry for the relocation of photon hits, a functionality necessary to reduce the photon losses that are observed in photon counting detectors due to charge sharing when the discrimination threshold is set to 50% of the photon energy. The circuitry is however not limited to full pixel relocation: it also implements resources to reassign X-ray hits within regions smaller than the physical pixel. All these operation modes were experimentally evaluated with a pencil beam and with full field images.

Design and evaluation of EMPIX2, a 100 kfps, high dynamic range pixel detector readout ASIC for electron microscopy

EMPIX2 is a novel hybrid pixel detector readout ASIC for electron microscopy with a maximum frame rate of 100 kfps and a very large dynamic range (5 × 105:1). It features 128 × 128 square pixels at a pitch of 150 μm. Adaptive gain switching and charge pump technology are applied to enhance the dynamic range. The pixels can operate in two modes: pulse mode and continuous mode. In pulse mode, ultra-fast gain switching enables a rapid response to pulsed electron sources, making it highly suitable for UEM applications. In continuous mode, the power consumption and dynamic range are optimized for STEM applications. The readout is frame-based, and digital image data is output by 64 pairs of LVDS drivers working in DDR mode at a clock frequency of 400 MHz. A dedicated data acquisition system was developed for the transmission and processing of the image data. Preliminary verification of the readout chip was performed using an on-chip calibration source.

Evaluation of planar silicon pixel sensors with the RD53A readout chip for the Phase-2 Upgrade of the CMS Inner Tracker

The Large Hadron Collider at CERN will undergo an upgrade in order to increase its luminosity to 7.5 × 1034 cm-2s-1. The increased luminosity during this High-Luminosity running phase, starting around 2029, means a higher rate of proton-proton interactions, hence a larger ionizing dose and particle fluence for the detectors. The current tracking system of the CMS experiment will be fully replaced in order to cope with the new operating conditions. Prototype planar pixel sensors for the CMS Inner Tracker with square 50 μm × 50 μm and rectangular 100 μm × 25 μm pixels read out by the RD53A chip were characterized in the lab and at the DESY-II testbeam facility in order to identify designs that meet the requirements of CMS during the High-Luminosity running phase. A spatial resolution of approximately 3.4 μm (2 μm) is obtained using the modules with 50 μm × 50 μm (100 μm × 25 μm) pixels at the optimal angle of incidence before irradiation. After irradiation to a 1 MeV neutron equivalent fluence of Φeq = 5.3 × 1015 cm-2, a resolution of 9.4 μm is achieved at a bias voltage of 800 V using a module with 50 μm × 50 μm pixel size. All modules retain a hit efficiency in excess of 99% after irradiation to fluences up to 2.1 × 1016 cm-2. Further studies of the electrical properties of the modules, especially crosstalk, are also presented in this paper.

Monte Carlo and experimental evaluation of a Timepix4 compact gamma camera for coded aperture nuclear medicine imaging with depth resolution

PurposeWe designed a prototype compact gamma camera (MediPROBE4) for nuclear medicine tasks, including radio-guided surgery and sentinel lymph node imaging with a 99mTc radiotracer. We performed Monte Carlo (MC) simulations for image performance assessment, and first spectroscopic imaging tests with a 300 μm thick silicon detector. MethodsThe hand-held camera (1 kg weight) is based on a Timepix4 readout circuit for photon-counting, energy-sensitive, hybrid pixel detectors (24.6 × 28.2 mm2 sensitive area, 55 μm pixel pitch), developed by the Medipix4 Collaboration. The camera design adopts a CdTe detector (1 or 2 mm thick) bump-bonded to a Timepix4 readout chip and a coded aperture collimator with 0.25 mm diameter round holes made of 3D printed 1-mm thick tungsten. Image reconstruction is performed via autocorrelation deconvolution. ResultsGeant4 MC simulations showed that, for a 99mTc source in air, at 50 mm source-collimator distance, the estimated collimator sensitivity (4 × 10−4) is 292 times larger than that of a single hole in the mask; the system sensitivity is 0.22 cps/kBq (2 mm CdTe); the lateral spatial resolution is 1.7 mm FWHM. The estimated axial longitudinal resolution is 8.2 mm FWHM at 40 mm distance. First experimental tests with a 300 μm thick Silicon pixel detector bump-bonded to a Timepix4 chip and a high-resolution coded aperture collimator showed time-over-threshold and time-of-arrival capabilities with 241Am and 133Ba gamma-ray sources. ConclusionsMC simulations and validation lab tests showed the expected performance of the MediPROBE4 compact gamma camera for gamma-ray 3D imaging.

Broadside-Coupled Niobium Flexible Cables

We have developed fine-pitch, multilayer, superconducting wiring for routing around a ninety-degree corner terminated with wirebonding interfaces. The component-level testbed for the Advanced Telescope for High Energy Astrophysics (ATHENA) X-Ray Integral Field Unit (X-IFU) focal plane requires compact, high-density, low-crosstalk wiring fanout to connect the detectors in the focal plane array with NIST-fabricated SQUID time domain multiplexing (TDM) readout chips. The full assembly baselines two interface chips: a flexible interface chip bending around the corner and a planar silicon carrier chip. The TDM readout is indium bump-bonded to the silicon carrier and afterward the flexible chip is clipped in place and wirebonded to the detector and fanout wiring on the carrier. This assembly is repeated for each side of the hexagonal focal plane structure. As conventional commercial cables are not able to achieve the fine-pitch, low-crosstalk, superconducting wiring required, we fabricate these flexible interface chips in-house via lithographic patterning and etching of sputter deposited thin films to create broadside-coupled superconducting niobium microstrips. Within the chip, the wiring on the flexible polyimide region transitions to silicon substrate for the closely spaced wirebond pads. The Nb microstrip wiring climbing a thick polyimide sidewall presents a fabrication challenge which we shall discuss in this paper. We describe the function of these components to build an effective engineering testbed for the ATHENA X-IFU.

Design of analog front-end integrated circuit of tactile sensor for human-machine interface

—In this paper, a highly integrated analog front-end chip for sensor data acquisition and readout is designed, which is applied to a pressure-to-capacitance-conversion 16 × 16 tactile sensor array. In this design, a 16-channel capacitance-to-digital converter using a combination of op-amp-based Capacitance-Voltage Converter (CVC) and column-parallel Single-Slope Analog-to-Digital Converter (SS ADC) converters has been implemented, increasing the readout speed of the sensor array and saving the chip area. In addition, a sequence of scanning circuit suitable for the 16 × 16 array is proposed, so that the CVC and column-parallel SS ADCs are in a pipelined working mode, which further improves the speed of data conversion and readout. The integrated circuit (IC) is designed and taped out in a 0.18-μm CMOS process technology. The measurement results show that the chip can reach the capacitance detection range from 1 pF to 9.1 pF, and it achieves a detection accuracy of 9 fF under 10-bit ADC quantization. Under the clock frequency of 64 MHz, the refresh rate of the entire array is 3906 fps, and the overall power consumption of the front-end IC is 7.5 mW.

Sub-1.4 cm3 capsule for detecting labile inflammatory biomarkers in situ.

Transient molecules in the gastrointestinal tract such as nitric oxide and hydrogen sulfide are key signals and mediators of inflammation. Owing to their highly reactive nature and extremely short lifetime in the body, these molecules are difficult to detect. Here we develop a miniaturized device that integrates genetically engineered probiotic biosensors with a custom-designed photodetector and readout chip to track these molecules in the gastrointestinal tract. Leveraging the molecular specificity of living sensors1, we genetically encoded bacteria to respond to inflammation-associated molecules by producing luminescence. Low-power electronic readout circuits2 integrated into the device convert the light emitted by the encapsulated bacteria to a wireless signal. We demonstrate in vivo biosensor monitoring in the gastrointestinal tract of small and large animal models and the integration of all components into a sub-1.4 cm3 form factor that is compatible with ingestion and capable of supporting wireless communication. With this device, diseases such as inflammatory bowel disease could be diagnosed earlier than is currently possible, and disease progression could be more accurately tracked. The wireless detection of short-lived, disease-associated molecules with our device could also support timely communication between patients and caregivers, as well as remote personalized care.

A common-mode suppression structure for absolute optical encoders

In traditional absolute optical encoders, the DC levels of the absolute code output signals are easily influenced by factors such as light intensity and temperature, leading to fluctuations in the duty cycles and errors in reading absolute code information. This paper presents a novel common-mode suppression structure for the readout of absolute code signals. By eliminating the common-mode component of the signals, the structure effectively suppresses common-mode interference and ensures that the duty cycles of the output signals remain close to the ideal value of 50%. To verify the effectiveness of the proposed common-mode suppression structure for absolute optical encoders, a photonic readout chip based on a 0.35μm CMOS process was designed, and good common-mode suppression effects can be achieved by combining the differential-distributed code disk. Test results show that when the LED’s normal operating current is 3.5 mA, the output duty cycle error is less than ±4%, which reduces 50% compared to the traditional structure. Under a variation of ±1 mA in LED operating current, the corresponding changes in output duty cycles remain within 5%. Similarly, when the temperature shifts from 25 °C to 125 °C, the changes in output duty cycles are contained within 3% It can be seen that this structure can suppress most of the common-mode interference caused by external factors, ensuring the stability of the output signals and reducing the bit error rate of the absolute code signals.

NTIMP1—A Fast Pulse Readout Chip With 1.2 V Power Supply Applied to the Diamond Detector in HIAF

A very fast pulse readout ASIC, NTIMP1, with 1.2 V power supply is presented in this work. It is going to be used as front-end electronics (FEE) for reading out the diamond detector signals in the TOF (Time of Flight) wall of RIBLL2 experiment of the High Intensity Heavy Ion Accelerator Facility (HIAF), China. So that an 8-channel fast front-edge readout chip named as NTIMP1 is proposed in this work. Each channel of NTIMP1 has a high-bandwidth preamplifier (with adjustable thresholds) dealing with differential current input, a fast hysteresis discriminator, and a LVDS (Low-Voltage Differential Signaling) module ensuring long-distance signal transmission. Fabricated with 0.13 μm standard CMOS Technology, NTIMP1 can get an input ranging from 2 fC to 2000 fC and the input impedance of the preamplifier can be adjusted externally with an off-chip resistor, so as to match with the electrode impedance of diamond detector. The bandwidth of the preamplifier is 495.5 MHz, which allows a very short signal peaking time of no more than 1 ns. The jitter of the leading edge is lower than 15 ps with 100 fC input charge suggesting that NTIMP1 is suitable for high-resolution TOF measurement as well as time-slewing correction.

A Sub-Electron-Noise Multi-Channel Cryogenic Skipper-CCD Readout ASIC

The MIDNA application specific integrated circuit (ASIC) is a skipper-CCD readout chip fabricated in a 65 nm LP-CMOS process that is capable of working at cryogenic temperatures. The chip integrates four front-end channels that process the skipper-CCD signal and performs differential averaging using a dual slope integration (DSI) circuit. Each readout channel contains a pre-amplifier, a DC restorer, and a dual-slope integrator with chopping capability. The integrator chopping is a key system design element in order to mitigate the effect of low-frequency noise produced by the integrator itself, and it is not often required with standard CCDs. Each channel consumes 4.5 mW of power, occupies 0.156 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> area and has an input referred noise of 2.7 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu\text{V}_{\text{rms}}$</tex-math> </inline-formula> . It is demonstrated experimentally to achieve sub-electron noise when coupled with a skipper-CCD by means of averaging samples of each pixel. Sub-electron noise is shown in three different acquisition approaches. The signal range is 6000 electrons. The readout system achieves 0.2 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${\text{e}^{-}}$</tex-math> </inline-formula> RMS by averaging 1000 samples with MIDNA both at room temperature and at 180 Kelvin.

Evaluation of HPK [formula omitted] planar pixel sensors for the CMS Phase-2 upgrade

To cope with the challenging environment of the planned high luminosity upgrade of the Large Hadron Collider (HL-LHC), scheduled to start operation in 2029, CMS will replace its entire tracking system. The requirements for the tracker are largely determined by the long operation time of 10 years with an instantaneous peak luminosity of up to 7.5 × 1034cm−2s−1 in the ultimate performance scenario. Depending on the radial distance from the interaction point, the silicon sensors will receive a particle fluence corresponding to a non-ionising energy loss of up to Φeq= 3.5 × 1016cm−2. This paper focuses on planar pixel sensor design and qualification up to a fluence of Φeq = 1.4 × 1016cm−2.For the development of appropriate planar pixel sensors an R&D program was initiated, which includes n+-p sensors on 150mm (6”) wafers with an active thickness of 150µm with pixel sizes of 100×25 µm2 and 50×50 µm2 manufactured by Hamamatsu Photonics K.K. (HPK). Single chip modules with ROC4Sens and RD53A readout chips were made. Irradiation with protons and neutrons, as well was an extensive test beam campaign at DESY were carried out. This paper presents the investigation of various assemblies mainly with ROC4Sens readout chips. It demonstrates that multiple designs fulfil the requirements in terms of breakdown voltage, leakage current and efficiency. The single point resolution for 50×50 µm2 pixels is measured as 4.0µm for non-irradiated samples, and 6.3µm after irradiation to Φeq = 7.2 × 1015cm−2.

TCT investigation of the one-sided depletion of low-temperature covalently bonded silicon sensor P-N diodes

In the context of particle detectors, low-temperature covalent wafer-wafer bonding allows for integration of high-Z materials as absorbing layers with readout chips produced in standard CMOS processes. This enables for instance the fabrication of novel highly efficient X-ray imaging sensors. In order to investigate the effects of the covalent bonding on the signal generated in such sensors, wafer-wafer bonded silicon-silicon P-N pad diodes have previously been produced. The behaviour of these test samples is being investigated with transient current technique (TCT) measurements. In this paper we present an overview of the TCT setup as well as a custom sandwich-type sample holder used for these measurements. A review of the results presented in a previous paper shows, that the bonded P-N structures show a highly asymmetric depletion behaviour under reverse bias. IR edge TCT measurements confirm that only the P-side of the samples is being depleted.