Differential serial interface scheme for high-speed image data transmission of mobile phones

Differential serial interface scheme for high-speed image data transmission of mobile phones

ROHM's Mobile Shrink DataLink (hereinafter referred to as MSDL) differential serial interface solution can greatly save the number of lines in the increasingly complex folding mobile phone clamshell connection. As LCD panels continue to move toward higher definition, more lines are required for mobile phone image data transmission, and high-speed data transmission will also generate electromagnetic wave interference. MSDL can not only solve the above similar problems, but also solve the problems encountered in mobile phone research and development. Many topics, so it will play a huge role in the application of folding mobile phones.

Figure 1: MSDL has a unique low-amplitude transmission mode.

Problems Faced by Foldable Mobile Phones In recent years, mobile phones are developing from the standard configuration of megapixel cameras to higher resolution camera configurations. Therefore, the amount of data processed inside the mobile phone is gradually increasing. Among them, the amount of image data is rapidly expanding due to the continuous high-quality and high-definition of liquid crystal panels and built-in cameras.

In a folding mobile phone, these image data transmission lines are generally connected between the application processor, the LCD panel and the camera through the flip connection, in this case, you will face the following two problems:

1. Users are asking mobile phone manufacturers to design mobile phones to be more novel and beautiful, so that new models of rotatable folding mobile phones and biaxial flips have appeared, and their housing structures are becoming more and more complicated. On the other hand, since a digital camera is arranged on the side of the liquid crystal panel, it is required to arrange more lines. The more lines make the product structure design more difficult, and at the same time it will seriously affect the reliability of the product, so solving these problems becomes an urgent issue.

2. Since the mobile phone needs to transmit data at high speed, the data line of the video signal at the flip connection will generate EMI. In order to reduce the influence of electromagnetic wave interference, it is necessary to strengthen the RF (wireless) characteristic attenuation countermeasures. The EMI emitted by the data line at the flip connection will increase as the data transmission rate increases. Usually the clamshell joint is placed near the antenna. In order to reduce the impact on the wireless characteristics, it is necessary to strengthen the countermeasures such as shielding or inserting a filter.



Figure 2: Current mode transmission used by MSDL reduces EMI.

Technical development of MSDL At present, as the interface of the LCD panel module of PC and LCD TV, the differential interface of low voltage differential signaling (LVDS) mode has become the global common standard specification. ROHM has already possessed first-class technology and management in the industry due to its advantages in high speed, low EMI, and low power consumption. Through the use of these technologies and mobile phone dedicated system LSI, ROHM has successfully developed MSDL, this new differential serial port can solve the problems encountered in the development of folding mobile phones. One such IC is used on the LCD screen circuit board and the host circuit board of the folding mobile phone (the IC converts the parallel data transmitted from the application processor to the liquid crystal panel into MSDL format), so that various functions can be realized.

MSDL uses current mode differential transmission technology, and the differential amplitude of the line part is transmitted with a small amplitude of tens of millivolts (Figure 1). The EMI characteristic is outstanding, and the noise level can be reduced by about 10dB compared with the previous CMOS transmission (Figure 2).

By reducing this EMI noise, two effects can be obtained: it does not adversely affect the RF (wireless) characteristics, and can also shorten the design period. The reason why reducing EMI noise can also shorten the design period is because it can reduce the process of solving the noise problem. Normally, in order to control EMI noise, mobile phone manufacturers will install anti-EMI components such as filters or shielding plates near the circuit of the flip connection to eliminate noise. However, because the impact of EMI noise in the actual use of mobile phones cannot be accurately estimated at the beginning of the design, in many cases, operations such as adjustment of filter characteristics or replacement of filter installation points must be continuously repeated, which leads to the design cycle. It often exceeds expectations and increases design development costs.

The receiver BU7285GU using this MSDL communication method can greatly save the line layout by performing image data MSDL transmission. For example, in the 18-bit color, QVGA size LCD panel interface, previously including the control signal line, need to deploy 22 dedicated lines for liquid crystal images, and if you use MSDL, you can reduce the number of lines to 7 (Figure 3). The following are the main features of BU7285GU series products:

1. MSDL greatly reduces the number of lines between the LCD panel and the CPU through the differential serial port method;

For example, the previous LCD interface: data + control signal line = 20, interface control line is 2. If you use a differential interface, you only need 6 + control signal lines, a total of 7 lines.


Figure 3: Example of a system based on BU7285GU.

2. Support 18-bit color, QVGA size LCD panel (can transmit 60fps);

3. Reduce the EMI noise generated by the line through the CMOS interface to about 10dB;

4. Adopt the light and thin package most suitable for mobile phone-VBGA063T050;

5. LCD I / F: support RGB stream;

Data, HS, VS, DCLK

Vdd (I / O) = 1.7? 3.3V (built-in level translation)

6. Built-in PLL: Generate serial transmission clock.

In the future, after supporting the 18-bit BU7285GU product of QVGA, ROHM is stepping up the research and development of other LCD data transmission products. At the same time, it will further research and development to support higher-definition LCD panels, support camera module interfaces, and support higher-speed data transmission Device. In the future, the newly developed mobile phone dedicated LSI and LCD driver interface will be configured in the mobile phone to meet the needs of customers for high-speed transmission, saving the number of lines, low EMI and low power consumption.

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Shenzhen Adela Technology Co., Ltd. , https://www.adelafiber.com