At present, for many popular mobile phones (especially clamshell mobile phones), the color LCD, OLED display or camera module CMOS sensor of the mobile phone are connected to the baseband controller through flexible circuits or long trace PCBs. The cable will be interfered by the parasitic GSM/CDMA frequency radiated by the antenna. At the same time, due to the introduction of high-resolution CMOS sensors and TFT modules, digital signals have to work at higher frequencies. These connecting lines will generate EMI interference like antennas or may cause ESD dangerous events. The above-mentioned EMI and ESD interference will destroy the integrity of the video signal and even damage the baseband controller circuit. Driven by the trend of compact design, considering the design constraints of board space, high filtering performance on mobile phone operating frequencies, and preservation of signal integrity, discrete filters cannot provide any space savings for the solution, and can only provide narrowband attenuation Limited filtering performance, so most designers currently use integrated EMI filters. As the resolution of LCD displays in portable devices such as mobile phones and cameras has increased, the transmission rate of video signals has also become higher and higher, and traditional filter solutions have slowly reached their technical limits. In a mobile phone equipped with a high-resolution display and an embedded camera, the signal is transmitted from the baseband ASIC to the LCD and the embedded camera at a specific frequency (depending on the resolution). The higher the video resolution, the higher the frequency of data work. For example, for a camera module with 30 to 600,000 pixels, the clock frequency is approximately between 6 to 12 MHz. Therefore, it is recommended to select the filter (upper and lower) cutoff frequency in the range of 30 to 50 MHz. With the increase in resolution to millions of pixels, the clock frequency has exceeded 60MHz, which requires the cutoff frequency of the filter to be as high as 300MHz. Figure 1: New filter unit structure (series resistance is 100 ohms, line capacitance is 20pF) Figure 2: New RC filter S21 parameter curve Figure 3: The structure of the British Union Electronics LC filter unit In the face of these development trends in the mobile phone industry, traditional RC filter solutions are reaching their limits. In order to meet the continuous increase of mobile phone video signals and the need for stronger ESD surge resistance, Yinglian Electronics has developed a new generation of EMI filters based on the LC structure. This integrated LC filter structure can be used to provide a cut-off frequency of up to 350MHz, and can support data rates with clock frequencies exceeding 60MHz. At the same time, it can provide excellent filtering performance, with attenuation characteristics better than -25dB in the frequency range of 800MHz to 2.5GHz. Figure 4 shows the S21 parameter index of the basic unit architecture of this filter. In addition to the filtering function, the integrated input TVS tube can also suppress up to 15kV air discharge ESD impact, reaching the performance level required by the IEC61000-4-2 level 4 industrial standard. Figure 4: S21 parameter curve of the British Union Electronics LC filter Inlink’s low-capacitance EMI filters UM4411, UM6411, UM8411 support 4-, 6- and 8-wire configurations, and each configuration includes a PI type RC filter network with a TVS tube connected to the side. The device uses a 0.4mm pin pitch QFN package, which can provide designers of ultra-thin mobile phones with a wider design space. Especially on the PCB layout, the current pin spacing of some display I/O connectors is 0.4mm. The use of 0.4mm pin spacing DFN package EMI filters will help system engineers to layout. In the selection of the device, a reasonable choice should be made according to the number of data channels. Figure 5 shows some advantages of using an 8-channel filter and two 4-channel filters on the layout; at the same time choose an 8-channel filter It is also lower than the cost of two 4-channel filters. Oilfield Gas Generator,Gas Power Generator,Green Power Gas Generator,Small Gas Generator Jiangsu Vantek Power Machinery Co., Ltd , https://www.vantekpower.com
