This paper serves as an introduction to USB Type-C and USB Power Delivery (PD) examining various applications and their data and power requirements.
Data and power roles![]() 1 | Typical data and power roles vary within end equipment with regards to the
USB Type-C specification. |
USB 3.1 Gen 1 (SuperSpeed) and Gen 2
(SuperSpeed+)![]() 2 | Applications that require transfer rates faster than 480 Mbps will need to
leverage either USB 3.1 Gen 1 (SuperSpeed) or Gen 2 (SuperSpeed+). |
USB Type-C pinout and
reversibility![]() 3 | The USB Type-C connector includes several new pins compared to USB Type-A
and Type-B connectors. |
The USB Type-C connector ecosystem addresses the evolving needs of modern platforms and devices, and the trend toward smaller, thinner and lighter form-factor designs. Additionally, the modification of USB PD for the Type-C connector helps address the needs of power-hungry applications.
You may have heard about USB Type-C’s reversible cable. When you think about the requirements for a particular system, however, you may be unsure about what’s necessary and what’s just “nice to have.” In this paper, we will introduce the most basic USB Type-C applications and work our way up to full-featured USB Type-C and USB PD applications. But first, let’s review the evolution of USB data, starting with USB 1.0 through USB 3.1 Gen 2.
Table 1 lists the maximum transfer rate of each USB data transfer-related specification. The standard started with USB1.x supporting 1.5 Mbps (low speed) and 12 Mbps (full speed), but evolved to support 10 Gbps (SuperSpeed+) with USB 3.1 Gen 2.
Specification | Data rate name | Maximum transfer rate |
---|---|---|
USB1.0 and USB 1.1 | Low Speed | 1.5 Mbps |
Full Speed | 12 Mbps | |
USB 2.0 | High Speed | 480 Mbps |
USB 3.0 | SuperSpeed | 5 Gbps |
USB 3.1 | SuperSpeed+ | 10 Gbps |
Table 2 shows the evolution of USB power, starting with USB 2.0 through USB PD 3.0. The overall trend has been to increase the maximum power to address the growing needs of platforms and devices. Without USB PD, you can support up to 5 V at 3 A (15 W) with just USB Type-C alone. However, with USB PD, you can support up to 20 V at 5 A (100 W) within the USB Type-C ecosystem.
Specification | Maximum voltage | Maximum current | Maximum power |
---|---|---|---|
USB 2.0 | 5 V | 500 mA | 2.5 W |
USB3.0 and USB 3.1 | 5 V | 900 mA | 4.5 W |
USB BC 1.2 | 5 V | 1.5 A | 7.5 W |
USB Type-C 1.2 | 5 V | 3 A | 15 W |
USB PD 3.0 | 20 V | 5 A | 100 W |
There are three types of data flow in a USB connection:
There are three types of power flow in a USB connection:
Figure 1 below highlights common end equipment and what their typical data and power roles are with regards to the USB Type-C specification.
The most simple and likely most common application is a UFP USB 2.0 without USB PD (≤15 W). Common applications include anything USB-powered today that does not require SuperSpeed data, such as a mouse, keyboard, wearables or various other small electronics. Figure 2 highlights the necessary functional blocks for a USB Type-C UFP USB 2.0 system.
At this point, we will assume that you understand the USB Type-C connector pinout and how reversibility works; if not, see Figure 13. Note that the USB 2.0 physical layer (PHY) is no different than previous USB 2.0 designs with a Type-A or Type-B connector. It serves as the physical layer between the data from USB’s D+ and D– lines to the USB 2.0 Transceiver Macrocell Interface (UTMI) plus low-pin interface (ULPI) for the application processor to manage.
USB 2.0 PHYs are often integrated into processors or microcontrollers; however, there are discrete PHYs available to integrate USB functionality into your design. The configuration channel (CC) logic block introduced in the USB Type-C specification determines cable detection, cable orientation and current-carrying capability.
The last block is a USB 2.0 multiplexer (often called a high- speed mux). The dotted outline in Figure 2 represents an optional block not required by the USB Type-C specification. To understand the purpose of the mux, it’s important to understand how flipping the cable affects data flow. In a USB Type-C receptacle, there are two pairs of D+/D– lines for a single channel of USB 2.0 data. In one orientation, data flows down one of the pairs. In the flipped orientation, data flows down the other pair. The USB Type-C specification allows shorting the pairs together, D+ to D+ and D– to D–, to create a stub. Although it’s not required, some designers elect to include a USB 2.0 mux in their system to improve signal integrity.
Texas Instruments (TI) offers a variety of devices for UFP applications with USB 2.0 data and no USB PD. These devices from TI offer a compact solution for CC logic that can determine cable detection, orientation and current- carrying capability.