A 6.9mW 120fps 28×50 capacitive touch sensor with 41.7dB SNR for 1mm stylus using current-driven ?S ADCs

Hyunseok Hwang, Hyeyeon Lee, Hongchae Kim, Youngcheol Chae

Research output: Chapter in Book/Report/Conference proceedingConference contribution

8 Citations (Scopus)

Abstract

Capacitive touch sensors are essential for the user interfaces of smartphones and tablet PCs. Large touch-screen panels (TSPs) require high-quality touch features, resulting in an increased number of sensing channels as well as a reduction of sensing capacitance due to fine-pitch arrangements. Therefore, touch-sensor ICs demand high resolution, low power and high efficiency. State-of-the-art capacitive touch sensors [1-6] mostly rely on capacitive charge amplifiers as analog front-ends (AFEs), which convert the capacitor change into a voltage signal and often limit the system noise figure, thus consuming most of the power. This paper presents a 120fps 28×50 touch sensor that achieves 41.7dB SNR for 1mm-φ stylus, while consuming 6.9mW, which results in an energy efficiency of 0.41nJ/step, for a >4× improvement compared to state-of-the-art stylus touch sensors (see Fig. 9.7.6). This is achieved by a current-driven ΔΣ ADC architecture, which implements charge balancing between a reference charge and a differential current from adjacent channels, directly interfacing with 2nd-order ΔΣ modulators. An area-efficient sinc2 filter, as a decimation filter, enables full parallel implementation of the 2nd-order ΔΣ ADCs, providing sufficient suppression of interference signals. In contrast to previous works, the current-driven ΔΣ ADC only needs to digitize small differential currents, which relaxes requirements of the front-end amplifier, resulting in a large power reduction.

Original languageEnglish
Title of host publication2017 IEEE International Solid-State Circuits Conference, ISSCC 2017
PublisherInstitute of Electrical and Electronics Engineers Inc.
Pages170-171
Number of pages2
Volume60
ISBN (Electronic)9781509037575
DOIs
Publication statusPublished - 2017 Mar 2
Event64th IEEE International Solid-State Circuits Conference, ISSCC 2017 - San Francisco, United States
Duration: 2017 Feb 52017 Feb 9

Other

Other64th IEEE International Solid-State Circuits Conference, ISSCC 2017
CountryUnited States
CitySan Francisco
Period17/2/517/2/9

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All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials
  • Electrical and Electronic Engineering

Cite this

Hwang, H., Lee, H., Kim, H., & Chae, Y. (2017). A 6.9mW 120fps 28×50 capacitive touch sensor with 41.7dB SNR for 1mm stylus using current-driven ?S ADCs. In 2017 IEEE International Solid-State Circuits Conference, ISSCC 2017 (Vol. 60, pp. 170-171). [7870315] Institute of Electrical and Electronics Engineers Inc.. https://doi.org/10.1109/ISSCC.2017.7870315