LCD Driver IC Research Articles

LCD 시스템을 위한 Current-Mode Multi-Valued Logic 인터페이스 회로

In this paper, we propose interface circuits for reducing power consumption and EMI when sequences of data from LCD controller to LCD driver IC by transmitting two bit data during one clock period. The proposed circuits are operated in current mode, which is different from conventional voltage-mode signaling techniques, and also employ threshold technique of Modified-LVDS(Low Voltage Differential Signaling) method. We have simulated the proposed circuits using H-SPICE tool for performance analysis of the proposed method. The simulation results show that the proposed circuits provide a faster transmission speed and stronger noise immunity than the conventional LVDS circuits. It might be suitable for the real-time transmission of huge image data in LCD system.

DSP를 이용한 모바일 TFT-LCD의 자동 감마 최적화 시스템 개발

This paper presents an automatic LCD gamma control system using gamma curve optimization. It controls automatically gamma adjustment registers in mobile LCD driver IC to reduce gamma correction error and adjusting time. The proposed gamma system contains Module-Under-Test (MUT, LCD module), PC installed with program, multimedia display tester for measuring luminance, and control board for interface between PC and LCD module. Proposed algorithm and program are applicable for most of the LCD modules. It is realized to calibrate gamma values of 1.8, 2.0, 2.2 and 3.0. The control board is designed with DSP and FPGA, and it supports various interfaces such as RGB and CPU. Developed automatic gamma control system showed significantly reduced gamma adjusting time of 240 sec. and much less average gamma error of 11% than 42h and 27% with conventional manual method. We believe that the proposed system is very useful to provide high-quality LCD and to improve production process.

72.4: Novel LCD Driver ICs with Built‐In Programmable RGB Independent Gamma Control

AbstractWe have developed a novel LCD driver IC with a programmable RGB Independent gamma‐curve control function. Our driver can control gamma‐curves of LCD panels with various gamma values. By setting only a few registers, detailed and accurate controls can be achieved. And, by correcting gamma‐curve of red, green and blue independently, driven LCDs have achieved high quality display images without the color shift.

P‐53: Spatio‐Temporal Level‐Adaptive Overdrive Method for LCD Driver ICs for Mobile Phone

AbstractWe developed a novel spatio‐temporal LAO processing method (ST‐LAO) that can be installed on LCD driver IC for a mobile phone by applying a novel edge‐enhancement processing to the linear approximation LAO method to reduce the LAO circuit size.

Implementation of LCD driver using asymmetric truncation error compensation for mobile DMB phone display

Small color LCDs have been widely used in the mobile display market for the past couple of decades due to their cost effectiveness. In particular, 64K color LCDs have gained in popularity over true color LCDs due to their low power consumption and effective transmission. However, the 24-bit to 16-bit image data conversion (referred to as asymmetric data truncation) results in a colorization of the gray scale and lack of smoothness, such as pseudo edge artifacts. Thus, to solve these problems, this paper proposes and implements a simple truncation error compensation algorithm using a 1-bit lower data expansion with neighbor pixel information. In experiments, the implemented LCD driver IC is shown to correct these artifacts .

LCD Module내 COF Bending에 따른 Lead Broken Failure의 개선

TCP(Tape Carrier Package), COG (Chip On Glass), COF(Chip On Film) are three methods for connecting LDI(LCD Driver IC) with LCD panels. Especially COF is growing its portion of market place because of low cost and fine pitch correspondence. But COF has a problem of the lead broken failure in LCD module process and the usage of customer. During PCB (Printed Circuit Board) bonding process, the mismatch of the coefficient of thermal expansion between PCB and D-IC makes stress-concentration in COF lead, and also D-IC bending process during module assembly process makes the level of stress in COF lead higher. As an affecting factors of lead-broken failure, the effects of SR(Solder Resister) coating on the COF lead, surface roughness and grain size of COF lead, PI(Polyimide) film thickness, lead width and the ACF(Anisotropic Conductive Film) overlap were studied, The optimization of these affecting manufacturing processes and materials were suggested and verified to prevent the lead-broken failure.

The improvement of the data overlapping phenomenon with memory accessing mode

Mobile phones use the embedded memory in LDI (LCD Driver IC). In memory accessing mode, data overlapping phenomenon can occur. These days, various contents such as DMB, Camera, Game are merged to phone. Accordingly, with more data transmission, there would be more data overlapping phenomenon in memory accessing mode. Human eyes perceive this data overlapping phenomenon as simply horizontal line noise. The cause of the data overlapping phenomenon was analysed in this paper. The data overlapping phenomenon can be changed by the speed of data transmission between the host and LDI. The optimum memory accessing position can be defined. This paper proposes a new algorithm for avoiding data overlapping.

Dual-Level LVDS Technique for Reducing Data Transmission Lines by Half in LCD Driver IC's

This paper proposes a dual-level low voltage differential signaling (DLVDS) circuit aimed at low power consumption and reducing transmission lines for LCD driver IC's. We apply two-bit binary data to the DLVDS circuit as inputs, and then the circuit converts these two inputs into two kinds of fully differential signal levels. In the DLVDS circuit, two transmission lines are sufficient to transfer two-bit binary inputs while keeping the conventional LVDS features. The receiver recovers the original two-bit binary data through a level decoding circuit. The proposed circuit was fabricated using a commercial 0.25μm CMOS technology. Under a 2.5V supply voltage, the circuit shows a data rate of 1-Gbps/2-line and power consumption of 35mW.

Development of a new automatic gamma control system for mobile LCD applications

This paper presents a new automatic LCD gamma control system using gamma curve optimization for the first time. Since conventional manual method depends on experiences of LCD module developers, it is highly labor intensive and requires several correction steps providing large gamma correction error. Proposed system controls automatically gamma adjustment registers in mobile LCD driver IC to reduce gamma correction error and adjusting time. The proposed gamma system contains module-under-test (MUT, LCD module), PC installed with program, multimedia display tester for measuring luminance, and control board for interface between PC and LCD module. We have developed a new algorithm using 6-point programmable matching technique with reference gamma curve. Developed algorithm and program are generally applicable for most of the LCD modules. It is realized to calibrate gamma values of 1.8, 2.0, 2.2 and 3.0. The control board is designed with DSP and FPGA, and it supports various interfaces such as RGB and CPU. Developed automatic gamma control system showed significantly reduced gamma adjusting time of 4 min. and much less average gamma error of 11% than 42 h and 27% with conventional manual method, respectively. We believe that the proposed system is very useful to provide high-quality LCD and to improve developing process using optimized gamma-curve setting.

無電解めっきバンプの形成と応用，評価

We have studied and learned that there are many advantages with the micro bump formation using the electroless plating method. Also the study on the usefulness of the process has been reported. This time we have experimented bonding TAB tapes on to the electroless plated bumps formed LCD driver IC. The results from the visual appearance seen from SEM photos and the break mode of the pull tests conducted on the bonded area shows that proper ILB conditions were found.

10 μA Quiescent Current Opamp Design for LCD Driver ICs

This paper examines the design considerations for an opamp to be used in a low-power consumption LCD driver IC: (1) slew rate enhancement suitable for a rail-to-rail input stage; (2) improved phase compensation with reduced compensation capacitance; and (3) limitation of instantaneous current consumption. The experimental results support our opamp design approach and indicate the feasibility of 10 μA quiescent current opamp.

Effects of the sampling pulse width on the frequency characteristics of a sample-and-hold circuit

Frequency characteristics, especially at high frequency, are important in applications such as sample-and-hold circuits for LCD driver ICs where the required signal bandwidth is much wider than the Nyquist rate. The frequency characteristics of a sample-and-hold circuit using analogue switches have hitherto been estimated from the frequency characteristics of a simple RC circuit comprising a storage capacitor and the on-resistance of the analogue switch. However, the effects of sampling pulse width and storage capacitor resetting are not taken into account. By giving an exact frequency-domain analysis of sample-and-hold circuits, the paper clarifies the limitations of conventional RC estimates. It also reveals the effects of storage capacitor resetting. A narrower pulse causes more ripples in the frequency characteristics. Storage capacitor resetting alleviates these ripples although the DC gain deteriorates for a narrow sampling pulse. This analysis was verified by simple experiments. A design for an LCD driver IC is also described as an application example.