1 Introduction
LED display is the main light-emitting diode (LED) driver chips and display unit by splicing of large-size flat panel display. The quality of the performance-driven chip on the LED screen display quality plays a vital role. In recent years, with the vigorous development of the LED market, many strong IC manufacturers, including Toshiba's *** (TOSHIBA), Sony (SONY), United States, Texas Instruments (T1), Taiwan's accumulated (MBl) and points Grain Science and Technology (SITl), and so on, began to produce special LED driver chips.
Driver type 2
LED Driver IC chips can be divided into general and two specialized chips. The so-called universal chip, the chip itself is not designed specifically for the LED, LED display, but some part of the logic function of logic chips (such as string - and to shift register). The ASIC means in accordance with the characteristics of LED light-emitting specifically designed for LED display driver chips. LED is the current characteristics of the device, that is saturated in the on-premise, its brightness as the current changes, rather than adjust the voltage at both ends of the change. Therefore, one of the largest dedicated chip features is to provide current source. LED current source can guarantee the stability of the drive to eliminate the flashing LED, LED display is a high-quality display screen on the premise. ASIC also some different sectors to increase the number of special features, such as adjusting brightness, error detection and so on. This article focuses on driver-specific chips.
2.1 General chip
General chip for general LED display of low-grade products, such as indoor monochrome screen, two-color screen and so on. The most common chip used is 74HC595. 74HC595 with 8-bit latch, the series - and to shift register and the three-state output. Each path can be the most 35mA of output current (non-current). IC manufacturers in general can produce such chips. Display commonly used in industry Motorola (Onsemi), Philips and ST, and other manufacturers of products, Motorola's performance better.
2.2 ASIC
ASIC has a large output current, such as the characteristics of the current, more applicable to the current, high-definition occasions, such as outdoor full-color, full-color indoor and so on.
ASIC's key performance parameters have the largest output current, output current source approach, the current output error (bit-bit, chip-chip) and data transfer clock, and so on.
● maximum output current
At present, the mainstream of current source of the largest chip multi-output current is defined as the largest single output current, generally about 90mA. Current ASIC is the most fundamental characteristics, but also get high-definition. At the same time, and each channel constant current maximum output (that is the biggest constant current output) for displays more meaningful, because in the white balance mode, each road requests are constant current output at the same time. The most general Current output current is less than the maximum allowed output current.
● current source output approach
The main source of constant current output approach, 8 (8-bit source) and 16 (16 sources) are two standards, 16 are basically the source of prevailing: TLC5921, TB62706/TB62726, MBl5026/MBl5016 and so on. 16-bit chip of the main sources of advantage lies in reducing the chip size, easy to drive LED board (PCB) routing, especially for smaller PCB-point distance is favorable.
● current output error
Current output error is divided into two types of error is between the current, that is the same for each chip output between the error; and the other is the current inter-chip error, that is, between the different chip output current error. Current output error is a critical parameter, the display of great influence on uniformity. The greater error, the worse the uniformity of the display, it is difficult to make the screen-white balance to achieve. At present, the mainstream of current source of chip-general of error between the current soil is less than 6%, inter-chip current error is less than - +15% o
● data transfer clock
Dedicated LED driver chip that contains all the basic functions of serial shift register functions, in order to achieve the data show that with the cascade of transmission, to build more large-size display at the LED display. Data show that the decision to shift the clock data transmission speed, data showed on the screen to update the rate has played a crucial role. As a large-size display, showing more than 85Hz refresh rate should be possible to ensure the stability of the screen (no flicker scanning flu). Higher data transfer clock is to obtain a high refresh rate display screen. At present, the mainstream of current source clock translocation frequency chips are generally in more than 15MHz.
2.3 At present, the mainstream of the LED chip performance
At present, LED display driver chip manufacturer dedicated mainly TOSHIBA (Toshiba), TI (Texas Instruments), SONY (Sony), MBI (accumulation of Science and Technology), SITI (point crystal technology). LED display in the domestic industry, which has several chip applications.
TOSHIBA products more cost-effective, in the domestic market share is also the highest. The main products TB62705, TB62706, TB62725, TB62726, TB62718, TB62719, TB62727, and so on. One TB62705, TB62725 is the source of 8-bit chip, TB62706, TB62726 is the source of 16-bit chips. TB62725, TB62726 are TB62705, TB62706 upgrade the chip. These products are in the current output errors (including inter-and inter-chip error), data transfer clock, the chip power supply voltage, as well as on improvements. As a mid-range chips, the current "TB62725, TB62726 has been gradually replaced TB62705 and TB62706. In addition, TB62726 there is a narrow-body TB62726AFNA package of chips, its width is only 6.3mm (TB62706 patch package of chips for the width of 8.2mm), This narrow body package more suitable for smaller space at the point of use on display. It should be noted that, AFNA package with the common package pin of a different definition of (anti-clockwise rotation of 90 degrees). TB62718, TB62719 is TOSHIBA market for high-end driver chips, in addition to current source with the general features of the chip, but also an increase of 256 gray mechanism (8-bit PWM), an internal current regulation, over-heated temperature protection (TSD) and the output open-circuit detection (LOD) and other functions. Applicable to high-end chips such the full-color LED display, of course, its price is also expensive. TB62727 for TOSHIBA new products, mainly in TB62726 on the basis of the increase in current regulation, temperature and alarm output open-circuit detection And other functions, and its market position in the range of TB62719 (718) and between TB62726, which is scheduled for October 2003 production.

TI as a world-class IC manufacturers, whose products do not use the natural properties of doubt. However, due to the early development of the Chinese LED market weak, the market share was not high. The main products TLC5921, TLC5930 and TLC5911 and so on. TLC5921 is a TSD, LOD function of the high-precision 16-bit source driver chip, the current inter-bit error is only ± 4%, but the price has been high, and only recently dropped to a very TB72726. TLC5930 with gray 1024 (10-bit PWM) of 12-bit chip source, with 64 features an adjustable brightness. TLC5911 is positioned to drive high-end chip market with a gray 1024, 64 adjustable brightness, TSD, LOD, and other features of the source of 16-bit chips. TLC5921 and TLC5930 chip in the bottom of the metal heat sink, when the practical application of LED lights to avoid the attention of the feet, otherwise they will cause leakage LED lights dimmed.
SONY has always been positioned as high-end product market, LED driver chip is no exception, the main products CXA3281N and CXR3596R. CXA3281N is the source of 8-bit chips, with a 4096 gray-scale mechanism (12 PWM), 256 brightness adjustment, the 1024 output current regulator, TSD, LOD and LSD (output short-circuit detection), and other functions. CXA3281N primarily designed for static drive mode, and its maximum output current is only 40mA. CXA3596R is the source of 16-bit chip functions CXA3281N inherited all the characteristics of the main purpose is to raise the output current (40mA increased by 80mA) output current source and approach (from 8 to 16). CXA3281N the current price of single-chip 1 U.S. dollars, CXA3596R price in more than 2 U.S. dollars.
MBI (accumulation of science and technology) products and TOSHIBA basically corresponds to the mid-range products, and pin functions are fully compatible, in addition to current source external resistors set the resistance is slightly different, basically a direct substitution can be used. The price of TOSHIBA lower than 10 to 20%, mid-range display is a good choice. MBI's MBl5001 and MBl5016 with TB62705 corresponding TB62706 and, MBl5168 1000 MBl5026 other points (j with TB62725 Wo Hau TB62726 counterparts. In addition, there have LOD function of its new products MBl5169 (8 bit source), MBl5027 (16 bit source ), 64 brightness adjustment function MBl5170 (8 bit source) and MBl5028 (16 bit source). LOD and a brightness adjustment function of chips used MBI's Share-I-OTM technology, chip and pin entirely without The function of these chips, such as MBl5168 and MBl5026 compatible. In this way, can not drive to change the board design can upgrade to the new.
SITI (point crystal technology) is Taiwan's R & D and production company specializing in LED driver chips, its performance and stability. Point crystal orientation and Technology TOSHIBA similar to the performance of their products and prices also. But do not pin-compatible. Crystal Point products are ST2221A, ST2221C, DMl34, DMl35, DMl36, DMl33 and ST2226A, and so on. In addition to the ST2221A for the 8-bit source, the other is the source of 16-bit chips. DMl34, DMl35 Wo Hau DMl36 is ST2221C upgrade products. This is the difference between three-chip output current is different, DMl34 output for the current 40-90mA, DMl35 output for the current 10-50mA, DMl36 output current for the 3-15mA. DMl33 with 64 adjustable brightness, LOD and the function of TSD. ST2226A with a 1024 gray mechanism (10-bit PWM), belong to high-end chips.
LED drive from several major chip manufacturers, product mix, the current constant current LED chip will consist of three grades. The first level is a gray-chip mechanisms, such chips PWM with internal body can produce gray-scale data input, the formation of more in-depth gray to high-quality images. The second level is a LOD, TSD, brightness adjustment function of the chip, the chip because of additional features and more applicable to the specific occasions, such as variable for the intelligence panels, with LED error detection function. The third file to function without any additional source of the current chips, such as the LED chip only to provide high-precision current source, to ensure that screen-display screen of good quality.
3, the main chip performance tables
According to the specifications provided by the five major manufacturers, from the logic functions, analog parameters such as chip packaging and on their LED chips are compared, such as Table 1 listed in Table 4.

4 Conclusion
We have developed a successful preparation for the p-channel polysilicon TFTAMOLED Step 6 of photomask technology. 6 step-by-step through the use of photomask technology, you can reduce costs and improve productivity. 6 step-by-step through the photomask process of the preparation of p-channel TFT, field-effect mobility of about 80cm2/Vsec, sub-threshold voltage swing is about 0.3V/dec, threshold voltage of about-2V. In the end, we use 6-step process photomask prepared 7-inch WVGA (720 * 480) AMOLED panel.