Universal Serial Bus 3.1 Specification, Revision 1.0
5.3 Connector Mating Interfaces
This section defines the connector mating interfaces, including the connector interface drawings, pin assignments, and descriptions.
5.3.1
5.3.1.1
USB 3.1 Standard-A Connector
Interface Definition
Figure 5-1 and Figure 5-2 show the USB 3.1 Standard-A receptacle and required ground spring mating areas, respectively. Figure 5-4 shows the Standard-A plug interface dimensions for USB 3.1. Only the dimensions that govern the mating interoperability are specified. All REF dimensions are informative.
The Universal Serial Bus Power Delivery Specifiation defines the mechanical and electrical requirements for the Insertion Detect feature to support cold socket capability. It may be
implemented in a Standard-A receptacle or a PD Standard-A receptacle. Implementation is vendor-specific. The Insertion Detect feature shall be implemented for cold socket Standard-A applications and is optional for all other Standard-A implementations. See the Universal Serial Bus Power Delivery Specifiation for complete Insertion Detect requirements. Example connector configurations including Insertion Detect features are shown in Figure 5-3.
Although the USB 3.1 Standard-A connector has basically the same form factor as the USB 2.0 Standard-A connector, it has significant differences inside. Below are the key features and design areas that need attention:
? In addition to the Vbus, D-, D+, and GND pins that are required for USB 2.0, the USB 3.1
Standard-A connector includes five more pins: two differential signal pairs plus one ground (GND_DRAIN). The two added differential signal pairs are for SuperSpeed data transfer, supporting dual simplex SuperSpeed signaling. The added GND_DRAIN pin is for drain wire termination and managing EMI, RFI, and signal integrity.
? The contact areas of the five SuperSpeed pins are located towards the front of the receptacle as
blades, while the four USB 2.0 pins towards the back of the receptacle as beams or springs. Accordingly, in the plug, the SuperSpeed contacts are beams located behind the USB 2.0 blades. In other words, the USB 3.1 Standard-A connector has a two-tier contact system.
? The tiered-contact approach within the Standard-A connector form factor results in less contact
area as compared to the USB 2.0 Standard-A connector. The connector interface dimensions take into consideration contact mating requirements between the USB 3.1 Standard-A receptacle and USB 3.1 Standard-A plug, the USB 3.1 Standard-A receptacle and USB 2.0 Standard-A plugs, and the USB 2.0 Standard-A receptacles and USB 3.1 Standard-A plug. ? The connector interface definition avoids shorting between the SuperSpeed and USB 2.0 pins
during insertion when plugging a USB 2.0 Standard-A plug into a USB 3.1 Standard-A receptacle or a USB 3.1 Standard-A plug into a USB 2.0 Standard-A receptacle.
? There may be some increase in the USB 3.1 Standard-A receptacle connector depth (into a
system board) to support the two-tiered-contacts as compared to the USB 2.0 Standard-A receptacle.
? Drawings for stacked USB 3.1 Standard-A receptacles are not shown in this specification.
They are allowed as long as they meet all the electrical and mechanical requirements defined in this specification. When designing a stacked USB 3.1 Standard-A receptacle, efforts need to be
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Mechanical
made to minimize impedance discontinuity of the top connector in the stack because of its long electrical path. Attention to the high speed electrical design of USB 3.1 Standard-A connectors is required. In addition to minimizing the connector impedance discontinuities, crosstalk between the SuperSpeed differential signal pairs and USB 2.0 D+/D- pair should also be minimized.
? The receptacle connector should have a back-shield to ensure that the receptacle connector is
fully enclosed. The USB 3.1 receptacle should also make good contact to the PCB ground by providing sufficient number of ground tabs to ensure a low impedance path to PCB ground. The USB 3.1 receptacle connector should have a robust mating interface to the shield of the USB 3.1 plug when it is inserted. Previous versions of this specification required providing a grounding spring tab in the middle of the side closest to the USB SuperSpeed signal contacts and grounding springs on both sides of the shell for USB 3.0 Standard-A receptacles. New designs shall have three grounding spring tabs on the side closest to the USB SuperSpeed signal contacts, two grounding spring tabs on the side opposite the USB SuperSpeed signal contacts, and a grounding spring on both sides of the shell of the USB 3.1 Standard-A receptacle. See Figure 5-2.
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Universal Serial Bus 3.1 Specification, Revision 1.0
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Mechanical
Figure 5-1. USB 3.1 Standard-A Receptacle Interface Dimensions
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Universal Serial Bus 3.1 Specification, Revision 1.0
TOP VIEW (SIDE NEAREST SUPERSPEED CONTACTS)
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USB - 3 - 1 - r1.0 协会尺寸规范
