PCB layout design for HDMI interface
PCB layout design, HDMI interface PCB, Impedance design PCB board
By: SYS Technology Co., Ltd.
The full name of HDMI is High Definition Multimedia Interface.
2. Line design requirements
Minimize attenuation by keeping the electrical length between the HDMI connector and the device as short as possible. In order for the differential signal to be transmitted normally, the two trace spacing of one differential signal must be consistent across the trace. Otherwise, variation in spacing will cause an imbalance in the magnetic field coupling, thereby reducing the effect of magnetic field elimination and causing an increase in EMI. The recommended line width ratio is 1:1 《W: S 《 1:2.
Because lines of different electrical lengths cause phase shifts between signals, they can also cause severe EMI. Ideally, the lengths of the four pairs of differential lines should be equal to ensure that the timing of signal transmission matches.
The internal error of the four pairs of differential lines is preferably within 5 mils, the error between pairs and pairs is preferably controlled within 10 mils, at the same time, the distance between pairs and pairs is required to be 15 mils, and try to distance if the space is allowed, reduce crosstalk.
3. Impedance design requirements
The differential impedance is controlled to 100 ohms (+/-10%) and the single-ended trace is controlled to 50 ohms. The goal of PCB design is to minimize discontinuous impedance as much as possible, thereby eliminating reflections and keeping the signal intact. The remaining inevitable discontinuities impedance should be grouped together, that is, the area of this area should be kept small and placed as close as possible. The idea is to focus each reflection point on a certain area instead of distributing it throughout the signal path.
4. ESD processing
The ESD components must be placed close to the HDMI terminal. But don't put it too close, consider the process requirements, and avoid the situation where the HDMI pad and the ESD components pad are easily tin-connection when soldering the HDMI terminal. The spacing is just the thickness of a soldering iron tip.
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SYS Technology Co., Ltd.