A brief discussion on the role of FLASH chips in LCD displays

In LCD displays , FLASH chips are often used to store data such as MCU programs and OSD menus. Common chips include MCU, 25×××, 24C××, 39LV001, 29FV, etc. This article systematically introduces the role of these chips in LCD displays.

1. Common chip types in LCD monitors

1. Commonly used MCUs in LCD displays

The development of LCD has gone through a process from multi-chip to single-chip. No matter which solution is adopted, MCU must be used to complete machine control and image display. The following introduces the commonly used MCUs for LCD.

The MCU used in LCD monitors and TVs is a single-chip microcomputer that integrates arithmetic units, controllers , memory (can also be external), and input and output functions. Commonly used ones are 4-bit (such as keyboard controllers, remote controls), 8-bit, 16-bit, and 32-bit (such as PDAs and other embedded devices). There are still two packaging forms: DIP and PLC C. The smallest single-chip microcomputer is the 8-bit PIC10F (6-pin, SOT-23 package) produced by MICROCHIP .

Under normal circumstances, the MCU's VCC power supply, OSC oscillation source, RESET reset, and ground terminal are all fixed, while the IO port function settings depend on the program. Therefore, in LCD repair, we often encounter the situation that even if the solution and chip are the same , the driver board uses different programs, and the image display is normal but the power on/off is invalid, or the power on/off can be turned on/off but there is no image display.

(1) NT68F63LG

This MCU is used in Samsung LCD models 510, 540, 710, 711, 712, 740, 911, 913, etc. The actual chip is shown in Figure 1. However, due to defects in this MCU, any LCD display using this model of MCU will fail after about 5,000 hours of use. The specific manifestation is: a black screen when receiving a signal (the indicator light is on, the power on/off is normal, and there is no image) or "non-optimal mode" is displayed on the black screen. The reason is not that there is an error in the program data in the MCU, but that the HV signal detection circuit of the MCU is damaged. At this time, the data in the faulty MCU is intact, and it can be read out and copied to the new MCU for use.

Note: The MCU used to copy data must be brand new. If you use a refurbished MCU, the above faults may still occur after soldering. Even if all are brand new MCUs, they will be damaged if soldered many times. Therefore, friends who are not very good at soldering can use the PLCC44 IC socket.

(2) MTV312MV64

This MCU is produced by MYSON and has encryption functions. HP and Golden Great Wall LCDs using this chip generally have their programs encrypted. All that is read out by the programmer is D4, and the MCU program cannot be backed up. The actual chip is shown in Figure 2. BenQ LCDs using this model of MCU are relatively common, and are commonly seen in the Q7T4 series. In actual maintenance, the failure rate of this MCU is very low.

(3) MTV512GMV

This MCU is also produced by MYSON and is commonly found in BenQ LCDs. It uses two packaging forms: PLCC44 and PQFP44. The actual chip is shown in Figure 3. The one used in the integrated screen of FP71G+ LCD is also MTV-512GMV.

(4) ALIM6759

This is the M6759 produced by ACER. The chip is shown in Figure 4. This MCU was mainly used in LCDs produced by AOC in the early days, mainly Lenovo, Founder, AOC, etc. The fault is that after a period of use, a black screen freezes and the power must be turned off to turn on/off. To solve this fault, a new MCU must be replaced. However, because this MCU was launched earlier, there are many refurbished MCUs on the market.

This fault is also a MCU hardware problem. There is no problem with the program in the old chip and it can be read out and continued to be used.

(5) M5964D

This MCU is used in DELL's 15-inch LCD and some online brand LCDs that use universal board solutions. The most commonly used are RTR2023, RTD-2013B, ZANE3SL, etc. of the universal board of Liquid Products. The actual chip is shown in Figure 5. This MCU cannot be read using programmers such as Xitel 3000U. Trying to read it will destroy the data in the MCU. The upgrade solution for this MCU is ISP, which is upgraded through the serial port or parallel port.

(6) W78E65

This MCU is commonly found in Lenovo, Founder and other LCDs. It is compatible with W78E062 and has a very low failure rate. The chip is shown in Figure 6. In actual maintenance, pay attention to anti-static when backing up or rewriting MCU data. The data in the chip can easily be damaged during the process of taking and placing the MCU, resulting in failure to turn on/off the machine.

(7) W78E065P

The actual chip is shown in Figure 7, and its performance is basically the same as W7E65.

(8) RTD2l20

This MCU is commonly found in ACER liquid crystal (PLCC package in Figure 8a) and is very popular in general driver boards (PQFP package in Figure 8b). The current RM345 1 and 2025 both use this MCU. This chip uses the ISP upgrade solution, which is convenient and simple to upgrade through VGA. However, the failure rate of machines using this solution is high, because the MCU completes key detection and HV signal detection at the same time, so it is easily damaged by static electricity, which is specifically manifested as invalid keypad and inability to recognize VGA signals.

(9) MXl0E8050

This MCU is commonly found in LCDs produced by Proview and its OEMs Lenovo, Founder, and Tsinghua Tongfang. This MCU is compatible with W78E65. The chip is shown in Figure 9. In actual maintenance, the failure rate of this MCU is low. Occasionally, the problem of internal program data loss may occur, which can be solved by rewriting.

(10) SM89516

This MCU is commonly found in early 15-inch LCDs and is interchangeable with AIM6759. The chip has a low failure rate and can be used to solve the black screen problem of M6759. The actual chip is shown in Figure 10.

(11) NT68F633LG

This MCU is commonly found in some models of LCDs from Tsinghua Tongfang and Lenovo. In actual maintenance, the failure rate of this MCU is not high, which may also be due to the fact that it is rarely used. The actual chip is shown in Figure 11.

(12) Weltrend WT61P4

This MCU is the MCU solution selected by Samsung to solve the problem after the failure of NT68F63LG in batches. It is commonly used in models such as 540N, 740, and 913. The actual chip is shown in Figure 12. This MCU is not compatible with Nr6sF63LG, and its failure rate is lower, but the cost is higher.

(13) Recent Yan chip solution DIP40 package

This solution is commonly seen in the recently launched single-chip TSUM16AK-LF solution. It is generally a driver, power supply , and high-voltage integrated board, and is used in unique, HP and other LCDs.

Regarding MCU substitution: In actual maintenance, it is impossible to prepare multiple MCU chips, so substitution is often considered. In actual maintenance, the DF data of MCU is difficult to find. A simple method can help us quickly find the MCU substitution model, which is to use a universal programmer. After the device is selected, use the adapter to obtain the MCU model in hand. If there is no error and the data can be read smoothly, it can be basically determined that the two MCU chips can be substituted. Moreover, this method will not damage the MCU chip and is very safe and reliable.

2. ROM chips commonly used in LCD color display

In the display, different types of FLASH chips are required to save OSD setting parameters and call preset display modes, enable the host to discover the display model, and store MCU program data.

(1) 24C16

On the LCD driver board, 24C16 is generally used to store the user mode and preset mode of the display, as well as the brightness , contrast , sharpness, color temperature and other data of the OSD panel adjusted by the user . The actual chip is shown in Figure 13. The preset data of the factory mode is also stored in 24C16. The more preset modes and user modes of the display, the larger the storage space of the chip. Therefore, we may see 24C32 and 24C08 used to store OSD data in actual maintenance.

The data in this chip is very important. If the data is accidentally damaged or lost, it will cause very strange malfunctions such as failure to boot, abnormal image, failure to detect signal, color cast, screen distortion, etc.

(2) 24C02

This chip is generally used to store information such as the monitor model, manufacturer, supported resolution type, and production date, as shown in Figure 14. This chip is generally located near the VGA and DVI interfaces and is used to complete information exchange with the PC host. If the VGA interface does not have this chip, the host will not be able to identify the monitor model and automatically match the resolution supported by the monitor, and can only display a plug-and-play monitor. However, the data of this chip near the VGA interface is damaged. It does not affect the operation of the monitor. Even if it is blank or not present, the monitor can still work normally. If the DVI interface does not have this chip or the data in the chip is damaged, the DVI interface device must be used after the computer is restarted, and cannot be used when the host is working normally. The model of this type of chip used in Samsung LCD is A21SC, which is read the same as 24C02.

(3) 24WC04

This chip is shown in Figure 15. It is mostly used to store OSD setting parameters. Its pin arrangement is the same as 24C02, 24C08, and 24C16. Moreover, this series of chips can be replaced by large-capacity ones.

(4) 24C08

Figure 16 shows two OSD parameter storage chips commonly used in Samsung LCDs. Although the models are A81SC and S24CS08, their read and write functions are the same as 24C08. They can be directly replaced with 24C08.

(5) 39LV010

This chip is shown in Figure 17. It is generally used in integrated MCU chip solutions, such as GM2110, GM5110 and other LCD displays, to store MCU programs. The storage space is 64kB and the operating voltage is +5V.

(6) 49LV010NT

The chip is shown in Figure 18 and is used in single-chip LCD solutions, such as GM2110, with a storage space of 64kB and an operating voltage of +3.3V.

(7) PM25LV010

In the LCD monitors launched in the past two years, all LCDs using single chips such as GM2621, GM5726, TS-UM16AL-LF, TSUM57AK, and TSUM-58 have an external 128kB memory to store MCU programs. The chip is shown in Figure 19. It has a storage space of 128kB and an operating voltage of 3.3V. The commonly used package for LCDs is SOIC8.

(8) Screen code

AUO and BOE's 17, 19, and 22-inch LCD panels all use 24C32 and 24C02 FLASH chips in SOIC8 and TSSOP8 packages to store the screen's operating parameter information, as shown in Figures 20 and 21. FLASH chips are also used on the widescreen LCD panels of the notebook 30P chip insert to store information such as the screen's manufacturer, production date, usage time, and operating parameters. If this information is rewritten or lost, the screen will not work. In other words, if this chip is missing or broken, the screen will not light up.

When we replace the screen of a laptop, if the screen interface is normal but the screen does not light up after replacement, we should consider replacing the chip (remove the chip of the broken screen and solder it to the new screen), or rewrite the chip information and data.

2. The role of the chip

1 MCU built-in storage space

Generally, independent MCU chips have a certain amount of built-in storage capacity, such as NT68-F63LG, MTV5l2GMV, etc., while multifunctional dedicated chips often use external storage space due to design packaging. Of course, for MCUs such as NT68F63LG, if the built-in storage space is insufficient, it can also be expanded through external memory. Chips such as TSUM16AK, TSUM56AL, TSUM57AK, TSUM-58AW are all LCD dedicated chips with built-in MCU functions. These chips require external 25XXX chips to store program codes.

2 MCU external FLASH is used to store MCU program

(1) 39 or 49 series memory chips

Machines using 39 or 49 series chips are generally GM2110 or GM2210 solutions, and are often seen in brands such as Philips , Lenovo, BenQ, and DELL. According to maintenance experience, the MCU program of this machine has fewer problems.

(2) 25 series memory chips

The machines using 25 series chips are monitors launched in the last two years. They are generally single-chip solutions, using solutions such as TSUM16, TSUM17, TSUM5c, TSUM57, TSUM58, GM-2621, GM5621, and GM5726. The chip integrates LVDS output, VGADA conversion, MCU, key control and other functions. The external 25XXX chip is used to store the MCU execution program code. In actual maintenance, the MCU program is rarely damaged.

3 OSD setting parameter storage chip 24C16, 24C32, 24C08, 24C04

All CRT and LCD monitors support multiple display modes, and can also store several user modes according to user preferences. The relevant setting parameters of these modes are stored in the 24CXX chip. The larger the capacity of the chip, the more factory modes and user modes can be preset.

In actual maintenance, there are many faults caused by data corruption in this chip, and the fault manifestations are also very complex.

4 VGA and host information exchange storage chip 24C02

We use LCD monitors, and the host can identify the monitor model and automatically set the display mode. The main reason is the existence of this chip. After the monitor is connected to the host, the host will access the graphics card through the SMB bus . The GPU will read the monitor through the 12th and 15th SDA and SOL buses of the VGA signal line, that is, read the data in 24C02. Only after completing the above data exchange action can the host correctly identify the monitor model and list the corresponding resolution according to the supported mode of the monitor.

If the chip is damaged or the 12th and 15th VGA signal lines are broken, the host will not be able to recognize the monitor and only "Plug and Play Monitor" will be displayed in the desktop properties.

5.DVI and host information exchange storage chip 24C02

The 24C02 data of the DVI interface is more important. Although DVI also supports plug-and-play, its plug-and-play is different from VGA. When the machine is turned on, the DVI signal line is invalid and the display will not produce images. We must connect the DVI signal line in the off state and then turn on the machine. Only in this way can the display work properly. Because after connecting the machine and powering on, the host also needs to read the information in the 24C02 of the DVI interface through the SCL and SDA buses. If the information in the chip is lost or damaged, the host cannot complete the data exchange with the display and the display cannot display.

6 OSD setting chip is stored in MCU

There is no FLASH chip on the driver board. The OSD menu related information is directly saved in the MCU. Part of the space in the MCU is used to store OSD related setting parameters.

3. Several common driver board solutions

1 BenQ G900HD (MCU+decoding chip)

This solution is MCU+decoding chip, as shown in Figure 22. The MCU completes HV signal detection, mode identification, key identification and other tasks, and the decoding chip is used to complete VGA signal analog-to-digital conversion and LVDS signal output functions.

2. Philips 170X6

This solution is a more traditional and common LCD driver board solution, which consists of LVDS output chip + MCU + external memory, as shown in Figure 23. GM5321 is a multifunctional chip that integrates MCU functions. The chip also completes the analog-to-digital conversion function of VGA and DVI. The driver board also has 39 chips to store MCU programs, 24C16 (DIP8) to store OSD setting parameters, and a 24C02 on each DVI and VGA interface to store display-related data.

3 GM5726 external memory

This solution is the most commonly used single-chip solution. Figure 24 is the driver board used by Samsung 943NW.