A 18V 69Mw 120Fps 50Channel Capacitive Touch Readout With Current Conveyor Afe And Currentdriven Delta Sigma Adc

• doi: 10.1109/JSSC.2017.2750326
• title: A 1.8-V 6.9-mW 120-fps 50-Channel Capacitive Touch Readout With Current Conveyor AFE and Current-Driven $\Delta \Sigma $ ADC
• publisher: IEEE
• isbn:
• issn: 1558-173X
• rank: 217
• access_type: LOCKED
• content_type: Journals
• abstract: This paper presents an area- and energy-efficient readout for capacitive touch sensors. An analog front end (AFE) with current conveyor mitigates the requirements of front-end opamp and provides a differential current from adjacent channels, removing sensor’s baseline and interferences. The sensing current from the AFE is directly digitized by a current-driven 2nd-order $\Delta \Sigma $ analog-to-digital converter and its direct interfacing with the current signal achieves high signal-to-noise ratio (SNR) without suffering voltage saturation in the AFE, and provides reconfigurable SNRs and frame rates with respect to oversampling ratio. An area-efficient sinc2 filter, whose filter coefficients are commonly provided, enables full parallel implementation of $\Delta \Sigma $ ADCs. A 50-channel prototype IC is fabricated in a 0.18- $\mu \text{m}$ CMOS process, occupying only 1.96 mm2. Using a 10.1-in $28 \times 50$ touch screen panel and a 3.3-V transmitter, this work achieves SNRs of 53.3 and 41.7 dB with finger and 1-mm- $\phi $ stylus, respectively, while drawing only 6.9 mW from 1.8-V supply at 120 fps. This results in the state-of-the-art figure-of-merit of 0.11 and 0.41 nJ/step for finger and 1-mm- $\phi $ stylus, respectively. Moreover, 500-dpi on-glass fingerprint sensor is verified with the same prototype IC and 15-V transmitter, and $70 \times 50$ fingerprint image is successfully captured with 150- $\mu \text{m}$ cover glass.
• article_number: 8051257
• pdf_url: https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=8051257
• html_url: https://ieeexplore.ieee.org/document/8051257/
• abstract_url: https://ieeexplore.ieee.org/document/8051257/
• publication_title: IEEE Journal of Solid-State Circuits
• conference_location:
• conference_dates:
• publication_number: 4
• is_number: 8241022
• publication_year: 2018
• publication_date: Jan. 2018
• start_page: 204
• end_page: 218
• citing_paper_count: 46
• citing_patent_count: 0
• download_count: 5583
• insert_date: 20170926
• index_terms:
  • ieee_terms:
    • Tactile sensors
    • Signal to noise ratio
    • Capacitors
    • Capacitance
    • Prototypes
    • Integrated circuits
  • author_terms:
    • Area-efficient decimation filter
    • capacitance-to-digital conversion
    • capacitive touch sensor
    • current conveyor analog front end (AFE)
    • current-driven delta-sigma analog-to-digital converter (ADC)
    • energy-efficient
    • incremental delta-sigma ADC
    • on-glass fingerprint sensor
  • dynamic_index_terms:
    • Frame Rate
    • Figure Of Merit
    • Figure-of-merit
    • Front End
    • Current Difference
    • Current Deviation
    • Capacitive Sensor
    • CMOS Process
    • Adjacent Channels
    • Direct Interface
    • Saturation Voltage
    • Touch Sensor
    • Transformer
    • Power Consumption
    • Differential Signal
    • Differentiation Signaling
    • Thermal Noise
    • Current Noise
    • Settling Time
    • Colonial Times
    • Supply Voltage
    • Bitstream
    • Binary Sequence
    • Charge Balance
    • Sinusoidal Signal
    • Charge Amplifier
    • Quantization Noise
    • Input Current
    • Charge Signal
    • Common-mode Rejection Ratio
    • Common Mode Rejection Ratio
    • Noise Immunity
    • Current Ratio
    • Offset Error
    • Gain Amplifier
    • Common Noise
• authors:
  • Author Name: Hyunseok Hwang
    Affiliation: Department of Electrical and Electronic Engineering, Yonsei University, Seoul, South Korea
    Author URL: https://ieeexplore.ieee.org/author/37382351100
    ID: 37382351100
    Order: 1
    Author Affiliations:
    • Department of Electrical and Electronic Engineering, Yonsei University, Seoul, South Korea
  • Author Name: Hyeyeon Lee
    Affiliation: Department of Electrical and Electronic Engineering, Yonsei University, Seoul, South Korea
    Author URL: https://ieeexplore.ieee.org/author/37086045359
    ID: 37086045359
    Order: 2
    Author Affiliations:
    • Department of Electrical and Electronic Engineering, Yonsei University, Seoul, South Korea
  • Author Name: Myungjin Han
    Affiliation: Department of Electrical and Electronic Engineering, Yonsei University, Seoul, South Korea
    Author URL: https://ieeexplore.ieee.org/author/37085577385
    ID: 37085577385
    Order: 3
    Author Affiliations:
    • Department of Electrical and Electronic Engineering, Yonsei University, Seoul, South Korea
  • Author Name: Hongchae Kim
    Affiliation: TRAIS, Ansan, South Korea
    Author URL: https://ieeexplore.ieee.org/author/37086044627
    ID: 37086044627
    Order: 4
    Author Affiliations:
    • TRAIS, Ansan, South Korea
  • Author Name: Youngcheol Chae
    Affiliation: Department of Electrical and Electronic Engineering, Yonsei University, Seoul, South Korea
    Author URL: https://ieeexplore.ieee.org/author/37274797400
    ID: 37274797400
    Order: 5
    Author Affiliations:
    • Department of Electrical and Electronic Engineering, Yonsei University, Seoul, South Korea

Image Sensor

• sensor_type: CMOS
• resolution: 1366x768
• dynamic_range: 53.3 dB (finger), 41.7 dB (1-mm φ stylus)
• pixel_size: Not specified
• dark_current: Not specified

Optical Data

• focal_length: Not specified
• aperture: Not specified
• field_of_view: Not specified
• distortion: Not specified

Performance Metrics

• frame_rate: 120 fps
• signal_to_noise_ratio: 53.3 dB (finger), 41.7 dB (1-mm φ stylus)
• power_consumption: 6.9 mW
• noise: 2.1 fF (standard deviation of input-referred capacitance offset for 50 channels)

Applications & Benefits

• cell_imaging: Used in capacitive touch sensors and on-glass fingerprint sensors.
• benefits: High energy efficiency for capacitive touch readout.

Supporting Organizations

• supported_by: Mid-career Researcher Program through NRF grant funded by the Ministry of Education, Science and Technology (MEST) under Grant 2014R1A2A2A09053061, National Research Foundation of Korea (NRF) Grant funded by the Korean Government (NRF-2017-Fostering Core Leaders of the Future Basic Science Program/Global Ph.D. Fellowship Program).

Manuscript Details

• publication_date: Jan. 2018

Relevancy Score

• score: 8
• missing_fields:
  • fill factor
  • quantum efficiency
  • readout speed
  • temporal noise
  • fixed-pattern noise
  • microlenses
  • on-chip colour filters
  • global or rolling shutters
  • backside illumination

Processed JSON Filename

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