Adiabatically driven touch controller analog front-end for ultra-thin displays

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 frontend 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 ΔΣ 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 sinc <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> filter, whose filter coefficients are commonly provided, enables full parallel implementation of ΔΣ ADCs. A 50-channel prototype IC is fabricated in a 0.18-μm CMOS process, occupying only 1.96 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . Using a 10.1-in 28 × 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-mmφ 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 × 50 fingerprint image is successfully captured with 150-μm cover glass.

SUMMARY This paper presents analysis and design of a new ultra-low voltage analog front end (AFE) dedicated to strain sensor applications. The AFE, designed in 0.18 μm CMOS process, features a chopper-stabilized instrumentation amplifier (IA), a balanced active MOSFET-C 2nd order low pass filter (LPF), a clock generator and a voltage booster which operate at supply voltage (Vdd) of 0.6 V. The designed IA achieves 30 dB of closedloop gain, 101 dB of common-mode rejection ratio (CMRR) at 50 Hz, 80 dB of power-supply rejection ratio (PSRR) at 50 Hz, thermal noise floor of 53.4 nV/ √ Hz, current consumption of 14 μA, and noise efficiency factor (NEF) of 9.7. The high CMRR and rail-to-rail output swing capability is attributed to a new low voltage realization of the active-bootstrapped technique using a pseudo-differential gain-boosting operational transconductance amplifier (OTA) and proposed current-driven bulk (CDB) biasing technique. An output capacitor-less low-dropout regulator (LDO), with a new fast start-up LPF technique, is used to regulate this 0.6 V supply from a 0.8–1.0 V energy harvesting power source. It achieves power supply rejection (PSR) of 42 dB at frequency of 1 MHz. A cascode compensated pseudo differential amplifier is used as the filter’s building block for low power design. The filter’s single-ended-to-balanced converter is implemented using a new low voltage amplifier with two-stage common-mode cancellation. The overall AFE was simulated to have 65.6 dB of signalto-noise ratio (SNR), total harmonic distortion (THD) of less than 0.9% for a 100 Hz sinusoidal maximum input signal, bandwidth of 2 kHz, and power consumption of 51.2 μW. Spectre RF simulations were performed to validate the design using BSIM3V3 transistor models provided by GLOBALFOUNDRIES 0.18 μm CMOS process.

Evaluation of Premium Ultrasound Systems With Sonographers: How Comparative Usability Testing Can Reveal Human Factors Issues Prior to Errors in the Exam Room1

Wireless communication networks span a wide range of applications such as traditional telephony, internet data access, and cyber-physical infrastructure monitoring. However, the quality of service is still lacking, and problems such as dropped calls, dead spots, and slow network speed are still very common. Those are due to fundamental constraints such as the scarcity of radio-frequency spectrum, signal propagation effects, e.g., channel fading and shadowing, and the small form factor of mobile devices with limited energy capacity and antenna diversity.

Smart lenses are detachable lenses connected to mobile devices via wireless networks, which are not constrained by the small form factor of mobile devices, and have potential to deliver better photo (video) quality. However, the viewfinder previews of smart lenses on mobile devices are difficult to optimize, due to the strict resource constraints on smart lenses and fluctuating wireless network conditions. In this paper, we design, implement, and evaluate an open-source smart lens, called Smart Beholder. It achieves three design goals: (i) cost effectiveness, (ii) low interaction latency, and (iii) high preview quality by: (i) selecting an embedded system board that is just powerful enough, (ii) minimizing per-component latency, and (iii) dynamically adapting the video coding parameters to maximizing Quality of Experience (QoE), respectively. Several optimization techniques, such as anti-drifting mechanism for video frames and QoE-driven resolution/frame rate adaptation algorithm, are proposed in this paper. Our measurement study shows that Smart Beholder outperforms Altek Cubic and Sony QX100 in terms of lower bitrate, lower latency, slightly higher frame rate, and better preview quality. We also demonstrate that sys adapts to network dynamics. Smart Beholder has been made public at http://www.smartbeholder.org as an experimental platform for researchers and developers to optimize smart lenses and other embedded real-time video streaming systems.

This paper presents a fully-differential touch screen panel (TSP) self-capacitance sensing (SCS) system with a self-capacitance mismatch calibration technique. Due to the self-capacitance mismatch of TSP, the analog front-end (AFE) of the receiver (RX) circuit suffers from dynamic range degradation and gain limitations, which lead to the signal-to-noise ratio (SNR) loss for the TSP SCS system. The proposed calibration introduces the difference in input resistance and the driving amplifier’s strength between the fully-differential input. Thus, the mismatch effect is efficiently relieved in terms of area and power consumption. The proposed calibration restores the SNR by dB even under the worst self-capacitance mismatch case.

Tangible user interface for touch screens, where interaction happens through tangible objects placed on the screen, is one possible option for addressing the lack of haptic feedback in touch screens. For the development of tangible user interface for mutual capacitance touch screens, it is of interest to be able to model how a tangible on the screen surface is seen by the touch screen controller. Finite Element Method simulations for this case is very demanding in terms of both computational resources and time. In this article, we present a computationally efficient model for simulating the capacitance image of arbitrarily shaped conductive sheets on full size mutual capacitance touch screen panels, with calculation time in the order of milliseconds. Output data from the model show good agreement with corresponding measurement data from experiments, with a root mean square deviation of 1.5% of the peak to peak of the measured values for the modeled screen area.

Interactive visual presentation of information can help an analyst gain faster and better insight from data. When combined with situational or context information, visualization on mobile devices is invaluable to in-field responders and investigators. However, several challenges are posed by the form-factor of mobile devices in developing such systems. In this paper, we classify these challenges into two broad categories - issues in general mobile computing and issues specific to visual analysis on mobile devices. Using NetworkVis and Infostar as example systems, we illustrate some of the techniques that we employed to overcome many of the identified challenges. NetworkVis is an OpenVG-based real-time network monitoring and visualization system developed for Windows Mobile devices. Infostar is a flash-based interactive, real-time visualization application intended to provide attendees access to conference information. Linked time-synchronous visualization, stylus/button-based interactivity, vector graphics, overview-context techniques, details-on-demand and statistical information display are some of the highlights of these applications.

This paper presents a high-resolution dual-integrating delta–sigma modulator (DI-DSM) for low-power analog front-end (AFE) circuits in biomedical instrumentation. The AFE contains a preamplifier and a switched-capacitor DS analog-to-digital converter. The proposed DI-DSM adopts two kinds of clock frequencies: one is the same as the conventional frequency and the other is one-half of the conventional frequency, which provides sufficient settling time for critical blocks. The proposed structure reduces harmonic distortions at the output of the preamplifier, since the preamplifier is given sufficient time to charge the sampling capacitor in the DSM. The use of a lower switching frequency at the critical blocks results in a significant reduction in the power consumption of both the preamplifier and the modulator. The proposed AFE chip is fabricated in a 65-nm CMOS process. The measurement results of the modulator show a peak signal-to-noise ratio (SNR) of 81.4 dB and a peak signal-to-noise-plus-distortion ratio (SNDR) of 80.4 dB, with a power consumption of 24.8 $\mu \text{W}$ at a supply voltage of 1 V and a signal bandwidth of 10 kHz. The complete AFE chip [which includes a preamplifier, a DI-DSM, a low-dropout (LDO) regulator, and a bandgap reference circuit (BGR)] shows a measured peak SNR of 79.3 dB and a measured peak SNDR of 77.0 dB with a preamplifier power of only 46.8 $\mu \text{W}$ (and 22.3 $\mu \text{W}$ for LDO, and 36.3 $\mu \text{W}$ for BGR).

This paper deals with the susceptibility to radio frequency interference (RFI) of the analog front ends embedded in smart power integrated circuits. The case of RFI injected in the power transistor terminals that propagates to the analog front ends of the same integrated circuit is investigated using equivalent circuits that include the silicon substrate. The demodulation of the interference that takes place in the analog front-end circuits is evaluated by means of an approximate nonlinear method. In particular, it is shown that the demodulation of the substrate interference in a MOS differential input stage depends on the asymmetry of the circuits connected to the input terminals. Based on this, a simple method to increase the immunity to such interference is presented and its effectiveness is proved through computer simulations and through measurements carried out on a test chip.

We report on a low cost, secure 2T-SONOS embedded nonvolatile memory (eNVM) using a novel contamination free process integration. The proposed 2T-SONOS cell utilizes reverse read method resulting in wide threshold voltage ( $\boldsymbol{V_{T}}$ ) window read margin. Using an eNVM on a 90 nm high voltage CMOS process, touch screen controller (TSC) embedded display driver IC application as well as wide input range TSC is possible. Unit cell shows 6 volt program and erase $\boldsymbol{V_{T}}$ window. However, 32 kB IP shows lower $\boldsymbol{V_{T}}$ window of 2 V due to cell $\boldsymbol{V_{T}}$ distribution, source side resistance and program disturb effect during programming. In case of programmed cells, both fresh and 1 k program/erase (P/E) cycled cells show abrupt initial $\boldsymbol{V_{T}}$ shift of 0.5 V after 48 hours of 120 °C bake test. However, erase $\boldsymbol{V_{T}}$ shift happened only at 1 k P/E cycled cell. Regardless of cycling and program/erase states, after 48 hours of bake, $\boldsymbol{V_{T}}$ shift was saturated. Thanks to the charge trap layer contamination suppressing novel process integration and optimized charge distribution, 120 °C data retention lifetime of over 10 years after 1k P/E cycling is obtained without using any special band gap engineered materials.

TDDI (Touch and Display Driver Integration) is a device that integrates two functions into one device. One function is as display driver IC and a second function is as a touch screen controller. For scaling to larger screen sizes for automotive applications with a TDDI architecture, multiple TDDI chips are needed due to the fan out of the required signals for supporting the display and integrated touch screen. However, in the case of TDDI multi‐chip architecture, synchronization among the plurality of chips becomes the key factor in order to achieve uniform picture quality and accurate touch response. For this paper we introduce techniques for synchronization for both the display and the touch function among a plurality of chips (TDDIs). In closing we have successfully achieved a cascaded TDDI architecture by this technique for a fully integrated automotive display and touch solution.

Touch sensing circuits for large touch screens require high resolution ADCs with high data rate for accurate and fast touch detection. This paper presents a third-order ΣΔ ADC design with an input bandwidth of 480 KHz at 61.44 MHz sampling frequency, the SNR and ENOB are measured to be 85 dB and 13 bits respectively. We present an efficient mixed signal design methodology consisting of circuit design, integration, and verification with analog and digital simulations. Using the proposed design methodology, the target ΣΔ ADC design is implemented with Dongbu 0.18-µm BDCMOS technology. The design results show its suitability for large mutual-capacitance touch screen controller applications.

This paper presents a new technique for reading out projected mutual capacitance touch screen panels. It models touch screen panel as a communication system. Orthogonal frequency division multiplexing (OFDM) is used along with time division multiplexing (TDM) to read out all channels of touch screen panels. Different carrier frequencies are applied to touch screen panel concurrently using OFDM, while the sensing lines are sensed sequentially using TDM. The proposed technique ensures a high frame scan rate by using simultaneous driving signals, and it provides high signal to noise ratio (SNR) by avoiding frequency band with high noise power. Simulation results demonstrate a SNR improvement of 8.2 dB by selecting adequate carrier frequencies.

Movement lets players improve their chances of winning. In board games, movement might involve moving one or more playing pieces a fixed or random distance determined by a spinner or dice. In a video game, movement involves controlling one or more playing pieces around a playing field using a keyboard, mouse, touch screen, or game controller.