• Title/Summary/Keyword: Auto-zeroing offset cancellation

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Touch Screen Sensing Circuit with Rotating Auto-Zeroing Offset Cancellation

  • Won, Dong-Min;Kim, HyungWon
    • Journal of information and communication convergence engineering
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    • v.13 no.3
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    • pp.189-196
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    • 2015
  • In this paper, we present a rotating auto-zeroing offset cancellation technique, which can improve the performance of touch screen sensing circuits. Our target touch screen detection method employs multiple continuous sine waves to achieve a high speed for large touch screens. While conventional auto-zeroing schemes cannot handle such continuous signals properly, the proposed scheme does not suffer from switching noise and provides effective offset cancellation for continuous signals. Experimental results show that the proposed technique improves the signal-to-noise ratio by 14 dB compared to a conventional offset cancellation scheme. For the realistic simulation results, we used Cadence SPECTRE with an accurate TSP model and noise source. We also applied an asymmetric device size (10% MOS size mismatch) to the OP Amp design in order to measure the effectiveness of offset cancellation. We implemented the proposed circuit as part of a touch screen controller system-on-chip by using a Magnachip/SK Hynix 0.18-µm complementary metal-oxide semiconductor (CMOS) process.

A Study on the Offset cancellation circuit using by using dual capacitor (Dual 커패시터를 이용한 Opamp 옵셋 저감 회로에 관한 연구)

  • Kim, Hanseul;Kang, Byung-jun;Lee, Min-woo;Son, Sang-Hee;Jung, Won-sup
    • Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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    • 2012.10a
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    • pp.848-851
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    • 2012
  • In this paper, circuit of reducing the offset voltage in Op-amp, effectively, is newly proposed by using dual capacitor. Capacitors and MOS switches are added in proposed circuit to make up for the weak points of previous circuits ofr reducing the offset voltage in auto-zeroing method. Also, it is designed to reduce the offset voltage in high frequency range by using chopping method, effectively. Circuit simulation and layout are executed by TSMC 1.8V, 0.18um process. From the simulation results, it is verified that magnitude of offset voltage is under 5mV and proposed circuit is good for compensation of offset voltage better than previous auto-zeroing method.

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