USB 2.0 Specification Engineering Change Notice (ECN) #1: Mini-B connector Date: 10/20/2000 Reason for ECN: The USB 2.0 specified device-side connector the B connector is too large for use with a new generation of handheld and mobile devices, e.g., cell phones which would benefit from connectivity to the PC. This ECN incorporates a specification of a device-side mini connector (hereafter referred to as a mini-B connector). The new connector only applies to upstream facing ports, i.e., connectors on devices. Summary of ECN: The bulk of the ECN specifies the mechanical requirements for the mini-B plug, receptacle and cable assembly. It also identifies the usage scope of this connector. The last part of the ECN describes the minimum test criteria and performance requirements for the new connector. Benefits of ECN: The ECN enables standardization of miniature device-side USB connectors and consequent economies of scales and lower cost for a new and growing class of devices which will benefit from connectivity to the PC. The standardization also allows leveraging of the compliance test and certification model which is already in place for USB connectors. Assessment of Impact on Current Specification and Current USB Products: The connector specified in the ECN will not have any impact on hardware or software of existing USB products. The current USB spec already allows for vendor-specific device side connectors such cable assemblies are called captive assemblies. All that the ECN does is to identify one such connector for use in devices which need the smaller size of connector. There is a potential for some end-user confusion because of two standard cable options; but this can be mitigated by appropriate end-user education. Structure of ECN: The ECN is in the form of a new Chapter 6 with the mini-B connector requirements inserted into the appropriate locations. This format enables specification of the new connector in context. Universal Serial Bus Specification Revision 2.0 85 Chapter 6 Mechanical This chapter provides the mechanical and electrical specifications for the cables, connectors, and cable assemblies used to interconnect USB devices. The specification includes the dimensions, materials, electrical, and reliability requirements. This chapter documents minimum requirements for the external USB interconnect. Substitute material may be used as long as it meets these minimums. 6.1 Architectural Overview The USB physical topology consists of connecting the downstream hub port to the upstream port of another hub or to a device. The USB can operate at three speeds. High-speed (480 Mb/s) and full-speed (12 Mb/s) require the use of a shielded cable with two power conductors and twisted pair signal conductors. Low- speed (1.5 Mb/s) recommends, but does not require the use of a cable with twisted pair signal conductors. The connectors are designed to be hot plugged. The USB Icon on the plugs provides tactile feedback making it easy to obtain proper orientation. 6.2 Keyed Connector Protocol To minimize end user termination problems, USB uses a “keyed connector” protocol. The physical difference in the Series “A” and “B” (or “mini-B”) connectors insures proper end user connectivity. The “A” connector is the principle means of connecting USB devices directly to a host or to the downstream port of a hub. All USB devices must have the standard Series “A” connector specified in this chapter. The “B” (or “mini-B”) “B” connector allows device vendors to provide a standard detachable cable. This facilitates end user cable replacement. Figure 6-1Figure 6-1 illustrates the keyed connector protocol. Universal Serial Bus Specification Revision 2.0 86 Series A ConnectorsSeries B Connectors Series A plugs are always oriented upstream towards the Host System Series B plugs are always oriented downstream towards the USB Device A Plugs (From the USB Device) B Plugs (From the Host System) B Receptacles (Upstream Input to the USB Device or Hub) A Receptacles (Downstream Output from the USB Host or Hub) Series mini-B Connectors Series mini-B plugs are always oriented downstream towards the USB Device mini-B Plugs (From the Host System) mini-B Receptacles (Upstream Input to the USB Device or Hub) Figure 6-1. Keyed Connector Protocol Universal Serial Bus Specification Revision 2.0 87 The following list explains how the plugs and receptacles can be mated: Series “A” receptacle mates with a Series “A” plug. Electrically, Series “A” receptacles function as outputs from host systems and/or hubs. Series “A” plug mates with a Series “A” receptacle. The Series “A” plug always is oriented towards the host system. Series “B” receptacle mates with a Series “B” plug (male). Electrically, Series “B” receptacles function as inputs to hubs or devices. Series “B” plug mates with a Series “B” receptacle. The Series “B” plug is always oriented towards the USB hub or device. Series “mini-B” receptacle mates with a Series “mini-B” plu