Design of analog pixels front-end active feedback

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The paper describes a design of a prototype chip in 28 nm CMOS technology, consisting of 8 × 4 pixels with 50 μm pitch, dedicated for the precise measurement of Time-of-Arrival (ToA) and Time-over-Threshold (ToT) with a resolution within the picosecond range. To address this requirement, in-pixel Vernier time-to-digital converter (TDC) has been implemented, which utilizes two ring oscillators per pixel. Overall chip architecture is introduced as well as pixel architecture and selected simulation results. The pixel consists of a recording channel and TDC part. The recording channel is composed of an inverter-based front-end amplifier with Zimmerman feedback, a discriminator, a calibration block and a threshold setting block. TDC part includes two ring oscillators together with their calibration blocks and additional logic with counters/shift registers that allow for precise ToA measurement (using Vernier method) as well as ToT measurement (using one of the oscillators). Alternatively, single photon counting (SPC) mode can be used. Frequency of oscillators is set in three steps. First, two global 8-bit digital-to-analog converters (DACs) are used for initial setting of all ring oscillators. Then, per-oscillator capacitance bank and 6-bit DAC are used for fine setting. Simulation results of core blocks suggest that the ToA resolution on the order of tens of picoseconds may be achieved. The chips are already fabricated and are currently being prepared for measurements.

Section: Introductionmentioning

confidence: 80%

Vernier time-to-digital converter with ring oscillators for in-pixel time-of-arrival and time-over-threshold measurement in 28 nm CMOS

Kadłubowski¹,

Kmon²

2021

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“…These techniques may be used in electron microscopy and antimatter research [7] as well as other precise time measurement applications [8][9][10]. There are many prominent examples of detectors that use these methods [8][9][10][11][12] and in this paper, we present an approach that is a continuation of our previous works [13][14][15][16][17].…”

Section: Introductionmentioning

confidence: 92%

Recording channel design for time-based measurements in 28 nm CMOS

Kadlubowski,

Kmon

2023

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In this paper we present a recording stage dedicated to time-based measurements required in imaging detectors. The prototype ASIC is manufactured in the 28 nm CMOS process and consists of a 8 × 4-pixel matrix of 50 μm pitch. Each pixel includes a recording stage that processes input signals for the digital circuitry, responsible for performing time-based measurements such as Time-over-Threshold and Time-of-Arrival. The digital part of the pixel is made up of two ring-based oscillators, configuration registers, and counters. The recording channel occupies only 12 × 50 μm while consuming 4.5 μA current. The in-pixel coarse and fine correction methods implemented allowed an improvement of gain and offset uniformity 3.3 and 10 times, respectively.

“…Its simplified schematic is shown in figure 1. It consists of a front-end amplifier with capacitive feedback and Zimmerman feedback [11,12]. The feedback capacitance is controlled using GAIN<0:1>, while the effective feedback resistance is controlled using the FEED<0:5> configuration bits.…”

Section: Recording Channelmentioning

confidence: 99%

Multichannel integrated circuit for time-based measurements in 28 nm CMOS

Kadlubowski,

Kmon

2024

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This paper discusses the application-specific integrated circuit prototype dedicated to readout of hybrid pixel X-ray detectors. The circuit is fabricated in 28 nm CMOS technology and occupies 1.1 × 1.1 mm2 of silicon area. Each of 8 × 4 pixels present in the prototype includes an analog front-end and a digital block with two ring oscillators and their supporting circuits. The circuit can operate in single-photon counting mode or time-based measurement mode. The paper discusses in detail the design decisions that influenced the final in-pixel ring oscillator architecture and layout. Measurement results are presented which demonstrate the performance of ring oscillators as well as regular operating modes of the chip: single photon counting and time-over-threshold measurement.