A 1.8-V 6.9-mW 120-fps 50-Channel Capacitive Touch Readout with Current Conveyor AFE and Current-Driven Δ Σ ADC

Hyunseok Hwang, Hyeyeon Lee, Myungjin Han, Hongchae Kim, Youngcheol Chae

Research output: Contribution to journalArticle

12 Citations (Scopus)

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 Δ Σ 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 Δ Σ ADCs. A 50-channel prototype IC is fabricated in a 0.18- μ mCMOS process, occupying only 1.96 mm2. Using a 10.1-in 28 × 50touch screen panel and a 3.3-V transmitter, this work achieves SNRs of 53.3 and 41.7 dB with finger and 1-mm- φ 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- φ stylus, respectively. Moreover, 500-dpi on-glass fingerprint sensor is verified with the same prototype IC and 15-V transmitter, and 70 × 50fingerprint image is successfully captured with 150- μ mcover glass.

Original languageEnglish
Article number8051257
Pages (from-to)204-218
Number of pages15
JournalIEEE Journal of Solid-State Circuits
Volume53
Issue number1
DOIs
Publication statusPublished - 2018 Jan 1

Fingerprint

Transmitters
Sensors
Glass
Operational amplifiers
Digital to analog conversion
Signal to noise ratio
Electric potential

All Science Journal Classification (ASJC) codes

  • Electrical and Electronic Engineering

Cite this

@article{83fa8104f58b42c09a3db326440aa13e,
title = "A 1.8-V 6.9-mW 120-fps 50-Channel Capacitive Touch Readout with Current Conveyor AFE and Current-Driven Δ Σ ADC",
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 Δ Σ 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 Δ Σ ADCs. A 50-channel prototype IC is fabricated in a 0.18- μ mCMOS process, occupying only 1.96 mm2. Using a 10.1-in 28 × 50touch screen panel and a 3.3-V transmitter, this work achieves SNRs of 53.3 and 41.7 dB with finger and 1-mm- φ 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- φ stylus, respectively. Moreover, 500-dpi on-glass fingerprint sensor is verified with the same prototype IC and 15-V transmitter, and 70 × 50fingerprint image is successfully captured with 150- μ mcover glass.",
author = "Hyunseok Hwang and Hyeyeon Lee and Myungjin Han and Hongchae Kim and Youngcheol Chae",
year = "2018",
month = "1",
day = "1",
doi = "10.1109/JSSC.2017.2750326",
language = "English",
volume = "53",
pages = "204--218",
journal = "IEEE Journal of Solid-State Circuits",
issn = "0018-9200",
publisher = "Institute of Electrical and Electronics Engineers Inc.",
number = "1",

}

A 1.8-V 6.9-mW 120-fps 50-Channel Capacitive Touch Readout with Current Conveyor AFE and Current-Driven Δ Σ ADC. / Hwang, Hyunseok; Lee, Hyeyeon; Han, Myungjin; Kim, Hongchae; Chae, Youngcheol.

In: IEEE Journal of Solid-State Circuits, Vol. 53, No. 1, 8051257, 01.01.2018, p. 204-218.

Research output: Contribution to journalArticle

TY - JOUR

T1 - A 1.8-V 6.9-mW 120-fps 50-Channel Capacitive Touch Readout with Current Conveyor AFE and Current-Driven Δ Σ ADC

AU - Hwang, Hyunseok

AU - Lee, Hyeyeon

AU - Han, Myungjin

AU - Kim, Hongchae

AU - Chae, Youngcheol

PY - 2018/1/1

Y1 - 2018/1/1

N2 - 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 Δ Σ 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 Δ Σ ADCs. A 50-channel prototype IC is fabricated in a 0.18- μ mCMOS process, occupying only 1.96 mm2. Using a 10.1-in 28 × 50touch screen panel and a 3.3-V transmitter, this work achieves SNRs of 53.3 and 41.7 dB with finger and 1-mm- φ 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- φ stylus, respectively. Moreover, 500-dpi on-glass fingerprint sensor is verified with the same prototype IC and 15-V transmitter, and 70 × 50fingerprint image is successfully captured with 150- μ mcover glass.

AB - 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 Δ Σ 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 Δ Σ ADCs. A 50-channel prototype IC is fabricated in a 0.18- μ mCMOS process, occupying only 1.96 mm2. Using a 10.1-in 28 × 50touch screen panel and a 3.3-V transmitter, this work achieves SNRs of 53.3 and 41.7 dB with finger and 1-mm- φ 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- φ stylus, respectively. Moreover, 500-dpi on-glass fingerprint sensor is verified with the same prototype IC and 15-V transmitter, and 70 × 50fingerprint image is successfully captured with 150- μ mcover glass.

UR - http://www.scopus.com/inward/record.url?scp=85030749260&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=85030749260&partnerID=8YFLogxK

U2 - 10.1109/JSSC.2017.2750326

DO - 10.1109/JSSC.2017.2750326

M3 - Article

AN - SCOPUS:85030749260

VL - 53

SP - 204

EP - 218

JO - IEEE Journal of Solid-State Circuits

JF - IEEE Journal of Solid-State Circuits

SN - 0018-9200

IS - 1

M1 - 8051257

ER -