A 1.8-V 128-Mb mobile DRAM with double boosting pump, hybrid current sense amplifier, and dual-referenced adjustment scheme for temperature sensor

To verify three important circuit schemes suitable for DRAMs in mobile applications, a 1.8-V 128-Mb SDRAM was implemented with a 0.15-/spl mu/m technology. To achieve an ideal 33% efficiency, the double boosting pump uses two capacitor's series connection at pumping phase, while they are precharged in parallel. The hybrid folded current sense amplifier together with a novel replica inverter connection improved power and speed performances. Also, a dual-referenced adjustment scheme for a temperature sensor was proposed to allow a very high accuracy in tuning. Without loss in productivity, the implemented dual-referenced searching technique achieved tuning error of less than /spl plusmn/2.5/spl deg/C.     

Variable structure observer of mismatched uncertain dynamical systems

To improve the steady state estimation error due to mismatched uncertainty, a variable structure observer for mismatched uncertain dynamical systems is proposed by using the generalised matrix inverse. Simulation results show that the estimation error is largely decreasing using the proposed observer.<>     

An ultraminiature CMOS pressure sensor for a multiplexedcardiovascular catheter

A multiplexed ultraminiature pressure sensor designed for use in a cardiovascular catheter is described. The sensor operates from only two loads, which are shared by two sensors per catheter. The sensing chip is 350 μm wide by 1.4 mm long by 100 μm thick. CMOS readout circuitry at the sensing site converts applied pressure to a frequency variation in the supply current, which is detected at the end of the catheter by a microprocessor-controlled interface. The nominal pressure sensitivity is 2 kHz/fF about a zero-pressure output frequency of 2.7 MHz. This on-site circuitry contains two reference capacitors which allow external compensation for nonlinearity and temperature sensitivity and has an idle-state power dissipation of less than 50 μW. With the transducer sealed at ambient pressure, the device can resolve pressure variations of about 3 mmHg, while vacuum-sealed devices do considerably better and should permit <2 mmHg resolution in practical systems     

A novel robust and low cost chips package and its thermalperformance

In an attempt to provide a high density memory solution, especially for workstation and PC servers, a stack chips package (SCP) has been developed. The major characteristics of SCP are as follows: (1) SCP contains a plurality of both memory chips and lead frames within a molded plastic package; (2) chip selection is made through the wire bonding option, resulting in the package with a memory capacity twice or four times that of monolithic chip; (3) plural lead frames are electrically interconnected all at once, using metal solders electroplated on the lead frame surface; and (4) SCP is found reliable and cost competitive when compared to other stack packages because it basically adopts the molded plastic packaging technology as well as the metal solder interconnection method. As electrical interconnection methods, both a fluxless soldering joint of Ag/Sn and a high-pressure mechanical joint of Ag were evaluated extensively and they successfully provided a reliable electrical conduction path without any signal degradation. Temperature cycle test and pressure cooker test were proved not to produce any micro cracks across the joint. The thermal performance of SCP was simulated by a thermal model based on finite element method (FEM) and also experimentally verified, showing good agreement within 10% deviation from simulated value. 128M SCP showed better thermal performance than stacked two TSOP's because one chip could serve as a heat sink while the other chip is activated and thermal conduction path through the lead frame is short     

Effects of channel thickness variation on bias stress instability of InGaZnO thin-film transistors

Here, we report on the effects of channel (or active) layer thickness on the bias stress instability of InGaZnO (IGZO) thin-film transistors (TFTs). The investigation on variations of TFT characteristics under the electrical bias stress is very crucial for commercial applications. In this work, the initial electrical characteristics of the tested TFTs with different channel layer thicknesses (40, 50, and 60 nm) are performed. Various gate bias (V_GS) stresses (10, 20, and 30 V) are then applied to the tested TFTs. For all V_GS stresses with different channel layer thickness, the experimentally measured threshold voltage shift (ΔV_th) as a function of stress time is precisely modeled with stretched-exponential function. It is indicated that the ΔV_th is generated by carrier trapping but not defect creation. It is also observed that the ΔV_th shows incremental behavior as the channel layer thickness increases. Thus, it is verified that the increase of total trap states (N_T) and free carriers resulted in the increase of ΔV_th as the channel layer thickness increases.     

Text-line extraction in handwritten Chinese documents based on an energy minimization framework

Text-line extraction in unconstrained handwritten documents remains a challenging problem due to nonuniform character scale, spatially varying text orientation, and the interference between text lines. In order to address these problems, we propose a new cost function that considers the interactions between text lines and the curvilinearity of each text line. Precisely, we achieve this goal by introducing normalized measures for them, which are based on an estimated line spacing. We also present an optimization method that exploits the properties of our cost function. Experimental results on a database consisting of 853 handwritten Chinese document images have shown that our method achieves a detection rate of 99.52% and an error rate of 0.32%, which outperforms conventional methods.     

Delay calculation capturing crosstalk effects due to coupling capacitors

A driver model to calculate gate and interconnect delays accurately for a chip with coupling capacitors is presented. The crosstalk effects between simultaneously switching victim and aggressors are effectively captured by iteratively solving an N-port RC network. The algorithm was implemented in a delay calculation tool called XINT and its accuracy demonstrated for industrial designs.     

CPW bandstop filter using slot-type SRRs

The bandstop characteristic of a slot-type split-ring resonator (SRR) on a substrate used for microwave frequencies is presented for a bandstop filter. Analogously to the conventional strip-type SRR, the slot-type SRR is very attractive for notching unwanted band because of its small dimension and high Q operation. In addition, the complementary SRR can be easily applied for coplanar configuration, which is favourable to MMIC designs. Based on the simulation and measurement results, the slot-type SRR for the bandstop filter is very effective in rejecting unwanted frequency in terms of its selectivity and size.     

N-channel thin-film transistors constructed on plastic by solution processes of HgSe nanocrystals

We demonstrate bottom-gate thin-film transistors (TFTs) based on solution-processed HgSe nanocrystals (NCs) on plastic substrates. Solid films made of spin-coated HgSe NCs were heated at a temperature of 150 °C for 15 min to maximize the magnitude of their current, and these films were utilized as the channel layers of TFTs. A representative TFT with a bottom-gate Al₂O₃ layer operated as a depletion-mode one with an n-channel, exhibiting a field effect mobility of 3.9 cm²/Vs and an on/off current ratio of about 10². In addition, the electrical characteristics of the TFT on bent substrates are briefly described.     

A movable safety zone scheme in urban fiber-optic microcellularsystems

We consider an urban fiber-optic microcellular system in which a cigar-shaped cell consists of several microzones with their own antenna sites connected to a central station through optical fibers. To increase the efficiency of radio resources and reduce unnecessary handoffs between microzones, we propose a movable safety zone scheme. A safety zone is a virtually guarded area that does not permit cochannel interference. Outside the safety zone, cochannels can be reused. The safety zone can move under the condition that its user does not meet cochannel interference as he moves to an adjacent microzone. Considering user mobility characteristics in the cigar-shaped cell, we analyze and evaluate the proposed system in terms of intracell and intercell handoff rates, blocking probability, intracell call-dropping probability, and channel reuse parameter. The proposed system can handle a traffic capacity of about 12 Erlangs for seven traffic channels under a call blocking probability of 1% and generates a negligible number of intracell handoffs compared with those of intercell handoffs