USB PCB Definition
Universal Serial Bus (USB) is a serial bus standard that connects computer systems and external devices, and is also a technical specification for input and output interfaces. It is widely used in information communication products such as personal computers and mobile devices.
And extended to photographic equipment, digital TV, game consoles and other related fields.
The new generation is USB 3.1, the transmission speed is 10Gbit/s, the three-stage voltage is 5V/12V/20V, the maximum power supply is 100W, and the Type C plug type is no longer divided into positive and negative.
USB PCB Design Points
The USB interface is placed close to the edge of the board, and extends out to a certain position on the edge of the board for easy plugging and unplugging.
ESD and common-mode inductance devices are close to the USB PCB interface, and the order of placement is ESD-common-mode inductance-resistor–capacitance; also pay attention to the distance between ESD and USB, leaving a distance of 1.5mm, considering the situation of post-soldering.
In order to suppress electromagnetic radiation, the differential lines of the USB are routed on the inner layer first, and ensure that the lines have a complete reference plane. Otherwise, splitting the traces will cause impedance discontinuity and increase the impact of external noise on the differential lines.
The USB must be differential, the impedance is controlled to 90 ohms, and the ground is included. The total length should not exceed 1800mil; the equal length method is similar to HDMI winding.
When the USB differential is routed, try to reduce the layer-changing vias as much as possible. The vias will cause discontinuity in the line impedance. Add a pair of return ground vias at each layer-changing hole for signal return. .
If the positioning posts on both sides of the USB PCB are connected to the protection ground, ensure that the distance from GND is 2MM when dividing, and drill more holes in the protection area to ensure sufficient connection, and use magnetic beads to bridge GND.+
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