Introduction

In the EU, a common charger regulation mandates that smartphones, tablets, digital cameras, headphones, portable game consoles, e-readers, keyboards, mice, and other eligible devices must support USB Type-C charging ports from December 28, 2024.Furthermore, from April 28, 2026, this will be expanded to include notebook PCs, and newly introduced notebook PCs in the EU market will need to support USB Type-C charging. This trend is not limited to the EU; various countries and regions are also considering and institutionalizing the adoption of USB Type-C as a common charging interface, and support for USB Type-C and USB Power Delivery is becoming an important prerequisite for product planning and design.
 
The purpose of this regulation is to reduce the number of different AC adapters and cables used for each device, thereby improving user convenience and reducing electronic waste from unnecessary chargers. In the EU, it is not prohibited to include an AC adapter when selling the product in question, but it is required that users be offered the option to purchase the product without an AC adapter, and that the charging specifications be clearly displayed on the packaging and in the sales information.Against this backdrop, it is expected that the use of sharing AC adapters among multiple devices will become even more common, and that even devices without built-in rechargeable batteries will increasingly adopt USB Type-C as their power supply port. The standard widely adopted for power supply using USB Type-C is USB Power Delivery, or USB PD for short. (Hereafter referred to as USB PD)
 
This article explains everything from the basic mechanisms of USB Type-C and USB PD, to the USB Type-C configuration process, the flow of power negotiation with USB PD, and an overview of the latest EPR standards and certification tests. Furthermore, it introduces key safety design points to keep in mind when developing USB PD-compatible devices, as well as recommended products from Renesas Electronics.

Various USB standards

The term "USB standard" encompasses three elements: "USB standards related to transmission speed," "connector shape," and "power supply."​

In this article, we will omit discussions of USB standards related to transmission speed, as these are separate from USB PD standards, and instead focus on standards related to connector shape and power supply.

connector shape

In the past, the dominant Type-A and Type-B connectors had different shapes for the host and device. The Type-C standard, announced in 2014, adopted a common shape for both hosts and devices. Furthermore, it became possible to use the connector without worrying about its orientation, and its shape is smaller than the previous Type-A and Type-B connectors.
 
On the other hand, even though Type-C connectors may look the same, it's important to note that they may support different standards. Clearly indicating the supported standard logo on both the connector and cable is not a mandatory requirement, and sometimes you can't tell if they'll work just by looking at them until you actually connect them.

Features of Type-C

With Type-C, new CC pins (Configuration Channel: CC1/CC2) have been added, enabling the following:

• The Type-C cable can be connected upside down.

- Both USB host and device can use Type-C ports.

- USB data, power, and video signals can be transmitted through a single cable.

Figure 1: Receptacle pinout       　　　　　　　　　　　　　　　　                        Figure 2: Plug pinout

The pin configurations of the receptacle on USB Type-C devices and the plug on USB Type-C cables are arranged symmetrically, as shown in Figures 1 and 2.

Figure 3: Internal structure of the CC line

In a USB Type-C cable, one end is connected to CC, and the other end is connected to GND via Ra within the cable. When the receptacle and plug are connected, the system determines which of CC1 or CC2 is used based on which of CC1 or CC2 is connected to CC.

Figure 4: Receptacle pinout

USB data lines (D+/D- for USB 2.0, Tx/Rx for USB 3.1) come in two pairs, but which data line is used depends on whether CC1 or CC2 of the receptacle is used. If CC1 is used, this data line is used.

Configuration process

When two USB Type-C devices are connected, the system first checks the voltage state of the CC pins (CC1/CC2) to determine whether the connected device is a source or a sink, the orientation of the cable, and the amount of current it can use. This entire process is called the configuration process.
 
The configuration process is a fundamental operation that is always performed even for USB Type-C devices that do not support USB PD​. Connection verification, role determination, and initiation of initial power supply are all determined by Rp/Rd. Furthermore, if both connected devices support USB PD, PD messages are exchanged on the CC line to determine whether higher voltage/current or Alternate Mode can be used.
 
Key point: The Source side pulls up the CC pin with Rp, and the Sink side pulls it down with Rd. The connection is only considered established when the Source detects Rd, and 5V is then supplied to VBUS. Therefore, if two Sources or two Sinks are connected, it will not be treated as a normal connection, and unnecessary power supply will not be initiated.
 
1. Detection of physical cable connection (Attach)
Before connection, the Source will, in principle, wait with its VBUS set to 0V. In this state, it monitors CC1/CC2 and, upon detecting the Rd of the connected device, determines that the Source and Sink are correctly connected. This allows the system to verify whether the connected device is capable of receiving power before starting power supply, even if the external Type-C connectors are the same.
2. Detection of the Plug surface
The USB Type-C receptacle has two pins, CC1 and CC2, but only one is actually used as CC on the cable side. The Source determines the plug's insertion direction (front or back) by checking which CC pin Rd appears on. Based on this determination, data line switching and internal multiplexer control are performed.
3. Source to Sink
Once the connection and orientation are confirmed, the Source begins supplying VBUS (usually 5V) to the Sink. At this stage, USB PD negotiation for higher voltages has not yet taken place. It starts with 5V as a safe initial state, and then transitions to 9V, 15V, 20V, etc., as needed through USB PD negotiation. In cables with e-Markers, the line on the side not used as CC may be used as VCONN. VCONN is used to supply power to the e-Marker and other components within the cable, and is important for confirming the cable's current capacity and supported functions.
4. Detection of the capability of the current value supplied from VBUS
​The Type-C current value notified to the Sink is determined by the Rp value connected to the CC pin of the Source. Typically, there are three patterns: Default USB Power, 5V/1.5A, and 5V/3A. Devices that do not support USB PD will control their current consumption within this notified range. Note that handling currents exceeding 3A or power in the EPR range requires negotiation via USB PD and confirmation of compatible cables.
5. Determining power conditions through USB PD negotiation
When two USB PD-compatible devices are connected, PD messages are sent and received over the CC line. Generally, the Source presents a list of available voltage and current options as Source_Capabilities, and the Sink returns the necessary conditions as Request. The Source then returns Accept, and once the voltage transition is complete, it notifies the Sink that it is ready with PS_RDY. These agreed-upon conditions are called a Power Contract.
6. Role Change and Alternate Mode Settings
USB PD not only determines the power supply conditions but also swaps roles such as Power Role Swap, Data Role Swap, and VCONN Swap as needed. Furthermore, for devices that perform video output or high-speed communication, it also negotiates Alternate Modes such as DisplayPort and Thunderbolt.
7. Actions to take when negotiations fail
If negotiations fail or the Source cannot supply the requested power, the Sink needs to be controlled to operate under lower power conditions, reduce the charging speed, or not start operating at all. During the design phase, it is important to check not only the expected AC adapter and cable, but also how the device will behave when incompatible or low-power devices are connected.
 
In summary, the USB Type-C configuration process is not simply about detecting that a connector has been inserted, but rather a mechanism for determining, step by step, the role of the connected device, the orientation of the cable, the available current, the cable's capabilities, and even the detailed power supply conditions when USB PD is supported. When this process is performed correctly, safe and appropriate power supply and communication can be achieved for each device, even if they have the same Type-C connector shape.

Direction of power supply

A Type-C cable can have Type-C connectors on both ends, but one end is recognized as the host and the other as the device, with power supplied from the host to the device. The USB PD standard allows for a feature called Dual Role Power (DRP). The power supply side is called the Source, and the power receiving side is called the Sink, and the roles of Source and Sink can be reversed. In other words, the direction of data communication and the direction of power supply can be set to be reversed.

EPR

If USB PD is supported, SPR can supply up to 100W and EPR up to 240W of power.Subsequently, with USB PD 3.2, concepts such as AVS (Adjustable Voltage Supply) were refined, making it important to design devices that can adjust the voltage more precisely to suit the device, rather than just using a fixed voltage.
 
The conventional range up to 100W is called USB PD SPR (Standard Power Range), and the extended range up to 240W is called USB PD EPR (Extended Power Range). When handling high power with EPR, a system design including compatible cables, controllers, and protection circuits is required.As of August 2026, USB-IF has released USB Power Delivery Specification Revision 3.2 Version 1.2 as a public specification, and it is important to match the referenced specification version, VIF settings, and firmware version during product development.

USB PD Power Rules

USB PD power rules are rules that organize which voltage and current PDOs (Power Data Objects) a USB PD-compatible source should present, depending on the power it can supply. The sink selects the necessary conditions from the candidates presented by the source and sends a request.
 
The table below summarizes the typical voltage and maximum current concepts used for each output power range. In the table, "x/20" represents the current value when supplying output power xW at 20V. For example, when supplying 45W at 20V, the current is 45W ÷ 20V = 2.25A.

How to read the table: SPR handles up to 100W, mainly using 5V, 9V, 15V, and 20V. A 5A cable is required for power exceeding 60W. EPR uses 28V, 36V, and 48V and supports up to 240W. To operate in the EPR range, the Source, Sink, and cable must all be EPR compatible.

About certification testing

Certification testing is a process to verify that a developed USB Type-C/USB PD compatible product conforms to USB-IF specifications. Obtaining certification makes it easier to demonstrate compliance with specifications externally and is also useful for confirming interoperability with AC adapters and cables from other manufacturers.
 
On the other hand, USB-IF certification is not mandatory for all products. For example, certification is particularly valuable if you want to use the USB logo, clearly demonstrate compliance with the specifications, or if your product is used in combination with various devices in the market. Conversely, for products with limited uses or connections, the decision of whether or not to obtain certification should be based on product specifications, sales region, customer requirements, costs, and development schedule.
 
Products that pass certification are listed on the USB-IF​ ​Integrators List, and can use the corresponding logo if they meet the requirements. However, there are separate licenses and usage conditions for using the logo. Therefore, beginners should first understand that "certification is not mandatory, but it is an important option if you prioritize logo usage, reliability, and interoperability."

Regarding safety

USB PD requires safety design, including overvoltage protection, overcurrent protection, overheating protection, and shutdown procedures in case of abnormalities, because it negotiates voltage, current, and power direction between devices before supplying power.
On the other hand, there are also Type-C shaped AC adapters and cables on the market that do not properly comply with the USB PD specification. Since it is difficult to determine the supported power and protocols from the appearance alone, it is necessary to consider how the device will behave when used in unexpected combinations. As a design policy, it is important to consider whether to assume that unexpected AC adapters and cables will not be used, or to consider the possibility of inappropriate combinations being connected and implement additional overvoltage, overcurrent, and overheat protection, connector anomaly detection, and firmware failsafe processing.

Recommended products

When developing USB Type-C/USB PD compatible products, it is necessary to consider not only keeping up with the latest specifications, complying with certification tests and regulations in various countries, but also the interoperability with power circuits, protection circuits, cables, and AC adapters.

For this type of development, it is crucial to select a total solution that combines not only a USB PD controller, but also a buck-boost charger/regulator control, evaluation board, configuration GUI tool, and firmware. Renesas Electronics' USB PD products include USB PD controllers such as the R9A02G011, Type-C port controllers such as the RAA489400, TCPM products such as the R9A02G015, and can be used in combination with buck-boost chargers/regulators, evaluation boards, and configuration tools such as VIDWriter / ImageGen. With easy configuration options ranging from SPR to EPR, Sink, Source, and DRP, it is easy to consider configurations tailored to your application. If you aim to shorten the development period for USB PD-compatible devices and streamline certification, please consider using Renesas Electronics products.

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