In order to ensure signal transmission quality, reduce EMI interference, and pass the relevant impedance test certification, PCB key signal impedance matching design is required. This design guide is based on the common calculation parameters, TV product signal characteristics, PCB Layout requirements, SI9000 software calculation, PCB supplier feedback information and so on, and finally come to the recommended design. Suitable for most PCB suppliers’ process standards and PCB board designs with impedance control requirements.

One. Double panel impedance design

① Ground design: line width, spacing 7/5/7mil ground wire width ≥20mil signal and ground wire distance 6mil, every 400mil ground hole; (2) Non-enveloping design: line width, spacing 10/5/10mil difference pair and the distance between the pair ≥20mil (special circumstances can not be less than 10mil) it is recommended that the whole group of differential signal line using enveloping shielding, differential signal and shielding ground distance ≥35mil (special circumstances can not be less than 20mil). 90 ohm differential impedance recommended design

Line width, spacing 10/5/10mil Ground wire width ≥20mil Signal and ground wire distance of 6mil or 5mil, grounding hole every 400mil; ②Do not include the design:

Line width and spacing 16/5/16mil the distance between the differential signal pair ≥20mil it is recommended that ground enveloping be used for the whole group of differential signal cables. The distance between the differential signal and the shielded ground cable must be ≥35mil (or ≥20mil in special cases). Main points: give priority to the use of covered ground design, short line and complete plane can be used without covered ground design; Calculation parameters: Plate FR-4, plate thickness 1.6mm+/-10%, plate dielectric constant 4.4+/-0.2, copper thickness 1.0 oz (1.4mil) solder oil thickness 0.6±0.2mil, dielectric constant 3.5+/-0.3.

Impedance design of two and four layers

100 ohm differential impedance recommended design line width and spacing 5/7/5mil the distance between pairs ≥14mil(3W criterion) note: it is recommended that ground enveloping be used for the whole group of differential signal cables. The distance between the differential signal and the shielding ground cable should be at least 35mil (not less than 20mil in special cases). 90ohm differential impedance Recommended design line width and spacing 6/6/6mil Differential pair distance ≥12mil(3W criterion) Main points: In the case of long differential pair cable, it is recommended that the distance between the two sides of the USB differential line wrap the ground by 6mil to reduce EMI risk (wrap the ground and not wrap the ground, line width and line distance standard is consistent). Calculation parameters: Fr-4, plate thickness 1.6mm+/-10%, plate dielectric constant 4.4+/-0.2, Copper thickness 1.0oz (1.4mil) semi-cured sheet (PP) 2116(4.0-5.0mil), dielectric constant 4.3+/-0.2 solder oil thickness 0.6±0.2mil, Dielectric constant 3.5+/-0.3 laminated structure: screen printing layer solder layer copper layer semi-cured film coated copper substrate semi-cured film copper layer solder layer screen printing layer

Three. Six layer board impedance design

The six-layer lamination structure is different for different occasions. This guide only recommends the design of the more common lamination (see FIG. 2), and the following recommended designs are based on the data obtained under the lamination in FIG. 2. The impedance design of the outer layer is the same as that of the four-layer board. Because the inner layer generally has more plane layers than the surface layer, the electromagnetic environment is different from the surface layer. The following are the suggestions for the impedance control of the third layer of wiring (laminated reference Figure 4). 90 ohm differential impedance Recommended design line width, line distance 8/10/8mil Difference pair distance ≥20mil(3W criterion); Calculation parameters: Fr-4, plate thickness 1.6mm+/-10%, plate dielectric constant 4.4+/-0.2, Copper thickness 1.0oz (1.4mil) semi-cured sheet (PP) 2116(4.0-5.0mil), dielectric constant 4.3+/-0.2 solder oil thickness 0.6±0.2mil, Dielectric constant 3.5+/-0.3 laminated structure: top screen blocking layer copper layer semi-cured copper-coated substrate semi-cured copper-coated substrate semi-cured copper-coated layer bottom screen blocking layer

For more than four or six layers, please design by yourself according to relevant rules or consult relevant personnel to determine the lamination structure and wiring scheme.

5. If there are other impedance control requirements due to special circumstances, please calculate by yourself or consult relevant personnel to determine the design scheme

Note: ① There are many cases that affect the impedance. If the PCB needs to be controlled by impedance, the requirements of impedance control should be clearly marked in the PCB design data or sample sheet; (2) 100 ohm differential impedance is mainly used for HDMI and LVDS signals, in which HDMI needs to pass the relevant certification is mandatory; ③ 90 ohm differential impedance is mainly used for USB signal; (4) Single-terminal 50 ohm impedance is mainly used for part of DDR signal. Since most DDR particles adopt internal adjustment matching impedance design, the design is based on the Demo board provided by the solution company as a reference, and this design guide is not recommended. ⑤, single-end 75-ohm impedance is mainly used for analog video input and output. There is a 75-ohm resistance matching the ground resistance on the circuit design, so it is not necessary to carry out impedance matching design in PCB Layout, but it should be noted that the 75-ohm grounding resistance in the line should be placed close to the terminal pin. Commonly used PP.