Ultrafast Largescale Chemical Sensing With Cmos Isfets A Levelcrossing Timedomain Approach

• doi: 10.1109/TBCAS.2019.2947167
• title: Ultrafast Large-Scale Chemical Sensing With CMOS ISFETs: A Level-Crossing Time-Domain Approach
• publisher: IEEE
• isbn:
• issn: 1940-9990
• rank: 3927
• access_type: LOCKED
• content_type: Journals
• abstract: The introduction of large-scale chemical sensing systems in CMOS which integrate millions of ISFET sensors have allowed applications such as DNA sequencing and fine-pixel chemical imaging systems to be realised. Using CMOS ISFETs provides advantages of digitisation directly at the sensor as well as correcting for non-linearity in its response. However, for this to be beneficial and scale, the readout circuits need to have the minimum possible footprint and power consumption. Within this context, this paper analyses an ISFET based pH-to-time readout using an inverter in the time-domain as a level-crossing detector and presents a 32 × 32 array with in-pixel digitisation for pH sensing. The inverter-based sensing pixel, controlled by a triangular waveform, converts the pH response into a time-domain signal whilst also compensating for sensor offset and thus resulting in an increase in dynamic range. The sensor pixels interface to a 15-bit asynchronous columnwise time-to-digital converter (TDC), enabling fast asynchronous conversion whilst using minimal silicon area. Parallel outputs of 32 TDC interfaces are serialised to achieve fast data throughput. This system is implemented in a standard 0.18 μm CMOS technology, with a pixel size of 26 μm × 26 μm and a TDC area of 26 μm × 180 μm. Additionally, we investigate the use of additional offset compensation by having half of the array implemented with the floating gate tied down via a well diode. Measured results demonstrate the system is able to sense reliably with an average pH sensitivity of 30 mV/pH, whilst being able to compensate for sensor offset by up to ±7 V. A resolution of 0.013 pH is achieved and noise measurements show an integrated noise of 0.08 pH within 2-500 Hz and SFDR of 42.6 dB. The total power consumption of the system is measured to be 11.286 mW when operating at a high frame rate of 1 KFPS.
• article_number: 8867938
• pdf_url: https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=8867938
• html_url: https://ieeexplore.ieee.org/document/8867938/
• abstract_url: https://ieeexplore.ieee.org/document/8867938/
• publication_title: IEEE Transactions on Biomedical Circuits and Systems
• conference_location:
• conference_dates:
• publication_number: 4156126
• is_number: 8948273
• publication_year: 2019
• publication_date: Dec. 2019
• start_page: 1201
• end_page: 1213
• citing_paper_count: 21
• citing_patent_count: 0
• download_count: 1176
• insert_date: 20191014
• index_terms:
  • ieee_terms:
    • Logic gates
    • Chemicals
    • Sensor arrays
    • Chemical sensors
    • Capacitance
    • Linearity
  • author_terms:
    • Chemical sensors
    • ISFETs
    • sensor interface
    • sensory arrays
    • time domain circuits
  • dynamic_index_terms:
    • Chemical Sensors
    • Ion-sensitive Field-effect Transistor
    • Ion Sensitive Field Effect Transistors
    • Power Consumption
    • Chemical System
    • pH Sensitivity
    • CMOS Technology
    • pH Response
    • pH Responsiveness
    • Chemical Imaging
    • Sensor Pixel
    • Readout Circuit
    • Time-to-digital Converter
    • Silicon Area
    • Pulse Width
    • Pulsewidth Modulation
    • Pulsewidth
    • Pulse Width Modulation
    • Chemical Signals
    • Thermal Noise
    • Current Noise
    • Supply Voltage
    • Sensor Array
    • Hot Electrons
    • Hot Carriers
    • Delay Line
    • Waveform Generator
    • Digital Output
    • Entire Array
    • Flicker Noise
    • Noise Performance
    • Signal Gain
    • Top Metal
    • Top Metallization
    • Total Capacitance
    • Large Offsets
    • Transistor Size
    • Transistor Count
    • Large-scale Array
• authors:
  • Author Name: Yan Liu
    Affiliation: Department of Micro-Nano Electronics, Shanghai Jiaotong University, Shanghai, China
    Author URL: https://ieeexplore.ieee.org/author/37537567000
    ID: 37537567000
    Order: 1
    Author Affiliations:
    • Department of Micro-Nano Electronics, Shanghai Jiaotong University, Shanghai, China
    • Department of Electrical and Electronic Engineering, Centre for Bio-Inspired Technology, Imperial College London, London, U.K.
  • Author Name: Timothy G. Constandinou
    Affiliation: Department of Electrical and Electronic Engineering, Centre for Bio-Inspired Technology, Imperial College London, London, U.K.
    Author URL: https://ieeexplore.ieee.org/author/37269841000
    ID: 37269841000
    Order: 2
    Author Affiliations:
    • Department of Electrical and Electronic Engineering, Centre for Bio-Inspired Technology, Imperial College London, London, U.K.
  • Author Name: Pantelis Georgiou
    Affiliation: Department of Electrical and Electronic Engineering, Centre for Bio-Inspired Technology, Imperial College London, London, U.K.
    Author URL: https://ieeexplore.ieee.org/author/37302145800
    ID: 37302145800
    Order: 3
    Author Affiliations:
    • Department of Electrical and Electronic Engineering, Centre for Bio-Inspired Technology, Imperial College London, London, U.K.

Image Sensor

• sensor_type: ISFET
• resolution: 32x32 pixels (each pixel is 26µm x 26µm)
• dynamic_range: Not specified directly, inferred to be significant due to design considerations.
• pixel_size: 26μm x 26μm
• dark_current: Not specified in the text.

Optical Data

• focal_length: Not applicable; ISFET does not utilize traditional lenses.
• aperture: Not applicable; ISFET does not use a lens system.
• field_of_view: Not applicable; ISFET arrays measure chemical properties, not fields of view like optical sensors.
• distortion: Not applicable.

Performance Metrics

• frame_rate: 1 KFPS (1000 frames per second)
• signal_to_noise_ratio: 42.6 dB
• sensitivity: 30 mV/pH (for normal pixels), 5.2 mV/pH (for diode pixels)
• shutter_speed: Not applicable; ISFET systems do not utilize shutter speeds.
• power_consumption: 11.286 mW during operation.
• noise: Integrated noise of 0.08 pH within 2-500 Hz.

Applications & Benefits

• cell_imaging: Used for applications such as DNA sequencing and fine-pixel chemical imaging systems.
• benefits: CMOS ISFETs provide advantages such as direct digitization at the sensor, compensation for non-linearity, minimal footprint, and reduced power consumption.

Supporting Organizations

• supported_by: Engineering and Physical Sciences Research Council (EPSRC), European Research Council under Synergy Grant 319818, i2MOVE.

Manuscript Details

• publication_date: Dec. 2019

Relevancy Score

• score: 10

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