Fiber optic transceivers, is a short twisted-pair electric signals and optical signals over long distances to swap the Ethernet transmission media conversion unit, in many places also known as the photoelectric Converter (Fiber Converter). The product is generally used in the actual network environment where the Ethernet cable cannot be covered and the optical fiber must be used to extend the transmission distance. For example, high definition video image transmission of monitoring security engineering; It has also played a big role in helping to connect the last kilometer of fiber optic lines to the WAN and beyond.
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LCM internal structure 
The internal structure of the STN-LCD color screen module is shown in Figure 1. Its upper part is an LCD screen composed of polarizers, glass, and liquid crystals. The lower part is a white LED and backlight board. It also includes the LCD driver IC and LCD. The driver IC provides a low-dropout voltage regulator (LDO) with stable power supply, two to eight white LEDs, and LED-driven boost regulator ICs.
LCM circuit structure 
The circuit structure of the STN-LCD color screen module is shown in Figure 2. The external power supply Vcc is stepped down and stabilized by the LDO to provide an operating voltage to the LCD driver IC such as Samsung's S6B33BOA, and it drives the LCD graphics and text of the color STN-LCD; external power supply Vcc is boosted and stabilized by the charge pump to provide constant constant voltage and constant current power to white LEDs such as 99-21UWC. The white light of the LED is reflected by the backlight board, so that the 65K color of the LCD liquid crystal is fully displayed, and the brightness of the LED directly affects the LCD. The beauty of the colors.
LCM main optoelectronic devices
l Colour STN-LCD
l LCD Driver: S6B33BOA
l LCD Driver LDO: AAT3221-2.8V AAT3221-3.0V
l White LED: 99-21UWC / TR8 99-215UWC / TR8
l LED Driver: AAT3110 AAT3113 AAT3123 AAT3134 NCP5007 NCP5008 / 9
l Backlight Board
LCD
LCD liquid crystal display is the abbreviation of Liquid Crystal Display in English. LCD is a type of flat panel display. It can be classified into three types: static drive (StaTIc), simple matrix drive (Simple Matrix), and active matrix drive (AcTIve Matrix). . Among them, the passive matrix type can be divided into twisted nematic (Twisted NemaTIc; TN), super twisted nematic (Super Twisted NemaTIc; STN) and other passive matrix driven liquid crystal displays; and the active matrix type can be roughly divided into Thin film transistor type (Thin Film Transistor; TFT) and two-terminal diode type (Metal / Insulator / Metal; MIM) two methods. TN, STN, and TFT LCDs have different levels of viewing angle, color, contrast, and animation display quality due to the difference in the twisting principle of liquid crystal molecules, which makes the application range of products also clearly differentiated. In terms of the current application scope and level of liquid crystal display technology, the active matrix drive technology is based on thin film transistor (TFT), which is mostly used in notebook computers and animation and image processing products. The simple matrix drive technology currently mainly uses twisted nematic (TN) and super twisted nematic (STN). STN liquid crystal displays can display three primary colors of red, green and blue through color filters, and then Through the harmonization of the three primary colors, the true color of the full-color mode can be displayed. At present, the application of color STN-LCD is mainly based on mobile phones, PDAs, digital cameras and video game console consumer products and word processors.
LCD driver IC
LCD driver ICs mostly use Hitachi and Samsung products. For example, Samsung ’s S6B33BOA is a 65K color saturation STN-LCD driver IC with good performance / price ratio.
Since consumer products of mobile phones, PDAs, digital cameras, and video game consoles are all powered by batteries, with the increase of use time, the power supply voltage fluctuates greatly, and the LCD driver IC requires a stable operating voltage, so the design of the circuit is often Provide a stable 2.8V or 3.0V voltage via a low dropout voltage regulator (LDO), such as AAT3221.
White LED
According to the design requirements of the backlight, white LEDs with low front drop voltage (VF), low front drop current (IF) and high brightness (500-1800mcd) are required. Take the mobile phone LCM as an example, currently use 3-4 white LEDs. With the increase in the brightness of LEDs and the requirements of mobile phone manufacturers to reduce costs and power consumption, it is expected that by mid-2004, LCM will use 2 high-brightness white LEDs (1200 — 2000mcd). PDA and Smartphone will use 4--8 white LEDs as needed due to the large LCD screen.
EL 99-21 / 215UCW / TR8 is a white SMDLED with good performance / price ratio and built-in reflector, its brightness is divided into three levels of T, S and R, T is 720-1000 mcd, S is 500-720 mcd are all suitable for mobile phone LCD backlight. Its quality is equivalent to NACW215 / NSCW335.
LED driver
The driving of the white LED needs to supply a constant voltage or a constant current, and the working voltage of the mobile phone power supply drops from the beginning, so a boost device is needed to boost and stabilize the voltage. In order to reduce the influence of the operating frequency of the boosting device on the radio frequency (RF) of the mobile phone, a capacitive charge pump that uses a capacitor as an energy transfer intermediate is generally selected; a booster that uses an inductor as an energy transfer intermediate can output a higher voltage.
The efficiency of the capacitive charge pump is divided into two kinds of frequency multiplication and fractional frequency multiplication according to its boosting method. The efficiency of the former is about 90%, the efficiency of the latter is about 93-95%; the efficiency of the inductive booster is about 83-85%; Capacitive charge pumps are divided into constant voltage output and constant current output according to their output; according to their method of driving LEDs, there are parallel constant voltage drive, single constant current drive, and series constant current drive; inductive boosters are all constant current Output, the output voltage is higher, and the LED is driven in series.
Frequency-doubled boosted capacitive charge pumps such as AAT3110, 5V constant voltage output, maximum current 120mA, parallel drive LED, as shown in Figure 3. 
A capacitive charge pump with a fractional doubling frequency boost, such as AAT3113, has 4-6 channels of constant current output, each channel can output 20mA current, and a single constant current drives LED, with 32-level dimming function, as shown in Figure 4. AAT3134 divides the output DAC module into two blocks, the output of which can drive the LCM module of dual screen display size. 
NCP5009 is a backlight LED drive booster with photosensitive sensor, suitable for automatic dimming high-end mobile phone LCM, which drives LEDs in series, as shown in Figure 5. NCP5007 is a backlight LED drive booster that can drive 5 series LEDs and PWM dimming in constant current, as shown in Figure 6. 
The new charge pump and booster have built-in MOSFETs inside the output, which can dynamically adjust the internal resistance of the load, eliminating the need for an additional constant current resistance due to the different internal resistance of the LED;
Capacitive charge pumps with a high switching frequency require small filter capacitors and low RF interference.
The capacitor is best to choose ceramic capacitors, because ceramic capacitors have no polarity and have a low equivalent series resistance (ESR), the typical value is less than 100mΩ. The equivalent series resistance value (ESR) of the ceramic capacitor, the quality of the dielectric material, and the size of the capacitance value have a significant impact on the output ripple. The X7R capacitor dielectric is the best and the cost is slightly higher; the X5R capacitor dielectric is centered and can be selected; the Y5V dielectric is poor and not recommended.
More and more mobile phones, PDAs, digital cameras and video game consoles use STN-LCD full-color displays. Therefore, the demand for STN-LCD color screen modules (LCM-LCD Module) has surged, and the quality of domestic LCD liquid crystal displays is already acceptable. Comparable with foreign countries, many mobile phone design and manufacturers began to require the use of LCD color screen modules produced by domestic LCD manufacturers. In 2001, 380 million mobile phones were produced worldwide, in 2003 it will grow to 430 million, and in 2005 it will grow to 520 million. In 2004, LCM color screen mobile phones will account for 35-40% of the total mobile phone output, so the annual demand for STN-LCD color screen modules (LCM) will increase to hundreds of millions.