USB Type-C端口的设计挑战与解决方案

 

Universal Serial Bus (USB) unifies many different types of connections and is ubiquitous in computers and consumer electronics. It has made it easier to connect multiple peripheral devices such as mice, cameras, printers, keyboards, external drives or other devices. Peripherals are no longer defined by their interface, and users no longer have to deal with multiple cable types to connect devices.

Compared to the maximum data rate of 12Mbps allowed by USB 1.1, USB 2.0 increases it to 480Mbps to handle a wide range of roles, including streaming video and quickly transferring data from an external device to a hard drive. Delivering up to 2.5W at 5V DC, the USB interface also enables users to power small devices such as external drives, laptops and cell phones without the need for an additional power supply.

Today‘s consumer trends are demanding higher bandwidth in smart products, such as HD streaming and 8K Ultra HD video, and exchanging data with high-speed hard drives. So new standards such as HDMI at 6Gbps, DisplayPort at 8.1Gbps and Thunderbolt at 20Gbps emerged.

Then the USB Implementers Forum (USB-IF) introduced the USB 3.2 specification, which identifies three transfer rates. USB 3.2 Gen1 (5Gbps), USB 3.2 Gen2 (10Gbps), and USB 3.2 Gen2x2 (20Gbps using a dual-channel physical interface). These products are sold to consumers as SuperSpeed USB 5Gbps, SuperSpeed USB 10Gbps and SuperSpeed USB 20Gbps.

Recently, USB4 has been specified to support transfer rates of 20Gbps (USB4 20Gbps) and 40Gbps (USB4 40Gbps). Backward compatible with USB 3.2, USB 2.0 and Thunderbolt 3, USB4 introduces several changes including a connection-oriented tunneling architecture that allows multiple protocols to be combined on the same physical interface and share the overall speed and performance of the USB4 architecture.

To support the new dual-channel high-speed specification while being backward compatible with USB 2.0 devices, a new physical interface is required. the USB Type-C (USB-C) interface not only integrates more connectivity for the two differential data channels and the USB 2.0 bus running in parallel, but also adds features to support the USB Power Delivery (USB PD) specification. These features include two sets of power and ground pins and a communication channel through which connected devices can negotiate their power consumption requirements and power supply capabilities ranging from the traditional USB 2.0 5V to the latest 20V/5A specification. Additional sideband usage (SBU) is also included to allow for future performance enhancements and new features.

 

# 1. USB-C Connector Pins (from Diodes)

From the user‘s perspective, USB-C simplifies the connection of devices. The connector is non-polarized, allowing the cable to be inserted in either direction upward; as a result, the USB-C connector has 24 pins to accommodate the large number of power and data connections needed to support USB 3.2, USB4 and USB Power Delivery (PD), and to allow backward compatibility with USB 2.0, as shown in Figure 1.

In addition, the interface is bi-directional, allowing the cable to have the same connector at both ends and allowing the connected device to act as a host or device or as a power consumer or provider.

Because of this flexibility and more pins, the USB-C interface is much more complex than its predecessor. Connected devices can be classified as downstream ports (DFP or source), upstream ports (UFP or receiver), or dual role ports (DRP) capable of providing and receiving data and power simultaneously. In each case logic is required to handle configuration control. It also needs to detect the direction of insertion of data lines and properly switch signals, such as USB 3.2 and DisplayPort to USB-C connectors. In addition, multiplexing USB 2.0 signals, power switching and charging control, and of course, signal integrity and transient voltage protection are required.

A device, such as a laptop or tablet, as shown in Figure 2, provides a fully functional USB-C interface capable of handling USB 3.2 and multimedia data and USB PD function.

 

# 2. USB-C connector Supporting USB 3.2 and USB PD in Laptops (from Diodes)

The USB power function is performed through the PD controller, which allows for up to 100W of power through the USB Type-C port, as well as an alternative mode for multimedia data through the USB Type-C port, as in the case of DP or Thunderbolt.

 

# 3. Implementing USB-C in Smartphones (from Diodes)

Figure 3 shows a USB-C port implementation for smartphones. The circuit combines USB Type-C configuration channel controller functionality with USB 3.2 Gen2 10Gbps multiplexing to enable proper data for non-polarized USB Type-C connectors. The device automatically configures host mode, device mode, or dual role ports based on the voltage level detected on the CC pins. It also provides connector orientation detection, as well as negotiation of charging current through the USB Type-C interface.

 

# 4. USB-C Application in Docks (from Diodes)

Figure 4 illustrates a universal docking station that connects to an upstream host via a USB Type-C port and provides DisplayPort, HDMI, VGA, and multiple USB 3.2 output ports for downstream devices such as displays and external storage. It also provides a Gigabit Ethernet LAN port. The power switch shown in the diagram enables the dock to supply power to the host via the VBUS pins. Outputs from the DP switch either go directly to the DP port or to the HDMI and VGA ports via HDMI or VGA converters.

Designers must confront the complexity of USB-C ports to take full advantage of the latest USB power and data features, including up to 100W power delivery, USB 3.2 and USB4 data rates, and multi-protocol support. A variety of integrated solutions are available to handle data switching, power switching, charge control, and cable orientation detection, simplifying design, facilitating product certification, and saving board space and material costs.