USB PD 3 Sink Controllers Power Up USB Type-C Applications

The window is quickly closing on proprietary device chargers, as regional regulators move to require a common charging solution based on a standard USB Type-C® cable and connector. Product designers racing to get ahead of regional requirements to meet this standard can optimize their applications for this new era by adopting USB Power Delivery (PD) sink controllers that negotiate power delivery between devices and chargers.

After December 2024, in the European Union, any wired, chargeable device requiring up to 100 W (laptops are temporarily exempt from the mandate until 2026) must utilize the USB Type-C chargeable port that complies with USB PD specifications. Other mandates for adopting that standard take effect in 2025 in India and Saudi Arabia, followed in 2026 by California.

USB Type-C alone can only deliver 5 V at 3 A, for a total of 15 W. Achieving 100 W requires USB PD 3.0 or USB PD 3.1 specifications, which ensure Type-C connectors can negotiate higher voltages while also transferring high-speed data.

USB PD 3.0 supports delivery up to 100 W and fixed voltages of 5 V, 9 V, 15 V, and 20 V, with a maximum current of 5 A. The updated USB PD 3.1 specification features an Extended Power Range (EPR) and Advanced Voltage Supply (AVS), boosting output power to as much as 240 W and adding three new fixed voltages of 28 V, 36 V, and 48 V.

The USB PD 3.x specifications improve on earlier PD 2.0 versions with an increase in the amount of information exchanged between a sink (the device receiving power) and a source (the device delivering power) to include factors that can impact the application, such as charging status of the device battery, battery temperature, failures, and overvoltage.

The 100 W of power delivered via USB PD 3.0 is sufficient to charge some laptops, monitors, and even some TVs. USB PD also supports video and audio output, including DisplayPort and HDMI, and data transfer protocols such as Thunderbolt 3.

Delivering enhanced applications

Product designers can take advantage of USB PD 3.x to deliver users a better experience with faster charging and data transfer, and device compatibility with a single cable and connector. They can stake a claim to reducing the e-waste that accumulates from consumer and business use of multiple cables and chargers to charge multiple devices.

The technology enables designers to simplify designs with fewer ports and components. Additionally, they may be able to reduce manufacturing and shipping costs through elimination of the weight and added packaging of chargers, as well as the time and effort required to update new device-specific chargers.

By using a single cable and connector for multiple functions, designers can focus on creating new and improved applications that leverage the high power and data rates of USB Type-C PD. They can also enhance the user experience and functionality of their products with additional features such as docking stations, hubs, and converters that expand the connectivity and compatibility of devices.

In developing new applications utilizing USB PD 3.0, product designers face some challenges, such as adhering to the USB PD specification and ensuring interoperability with other devices and chargers.

Preventing damage or injury from overvoltage, overcurrent, or reverse polarity is another critical issue, particularly as solutions using this technology utilize more complex circuitry and firmware than earlier generations. Helping to overcome such challenges are power delivery controllers that support multiple protocols and configurations, and evaluation boards that enable rapid prototyping and verification.

Putting USB Type-C PD to work

A key to USB PD 3.0 is the ability to negotiate and manage power delivery between a sink and a power source using a standardized protocol. USB PD sink controllers negotiate with a USB PD source, e.g., a charger, to acquire a device's power profile. Compliant devices can request and supply different voltages and currents according to their needs and capabilities and dynamically adjust power levels during operation.

The power delivery negotiation and management process consists of four stages:

• Discovery occurs when the sink and source identify each other as USB PD compatible devices and establish a data communication channel over the configuration channel (CC) pins on the USB Type-C connector.
• Capability exchange is when the source identifies its supported power profiles—voltage and current levels—to the sink, which then requests a profile that matches its requirements.
• Power contract is a process for the source to accept or reject the sink's request. If accepted, the source begins to supply the requested power to the sink utilizing the agreed-upon power parameters.
• Power rule update enables the sink or the source to initiate a new power negotiation to accommodate changes to battery levels or load on the sink, or changes to the source's input power.

USB PD 3.0 utilizes extended messages, governing the exchange of information between a sink and a source, such as battery status, temperature, or manufacturer-specific data. It also supports programmable power supply (PPS) mode, enabling finer-grained control of source output voltage and current, and seamless switching of power roles between the sink and source without disrupting data communication.

Another key capability of USB PD 3.0 is reverse charging, which allows a device with higher battery capacity to charge a device with lower battery capacity, regardless of their power roles. So, for example, using the same USB Type-C cable, a laptop can charge a smartphone, or that same smartphone can charge a headset, an obvious benefit to device users who can carry one cable for charging multiple devices.

Reverse charging may not be compatible with all devices or chargers. Additionally, it can result in reduced battery life of the device functioning as the source and increase the complexity and cost of the circuit design. So, as with all electronic applications, product designers must weigh the trade-off of implementing reverse charging to ensure they are complying with the USB PD 3.x specifications, and test interoperability with a range of devices and chargers.

USB 3 Sink Controllers

To enable USB PD 3.x functionality in their devices, product designers can use dedicated sink controllers that support the protocol and handle the communication with the source device.

Diodes Incorporated offers highly integrated and cost-effective solutions that provide fast charging, reverse charging, PPS mode, and other features of USB PD 3.x. They also support legacy protocols such as Qualcomm Quick Charge 4+ and Huawei FCP/SCP, ensuring compatibility with a wide range of chargers and adapters.

The AP33771 (Figure 1) is a USB PD 3.0 controller that features USB PD 3.0 compliant firmware and an interface with a preloaded power menu, making it simpler to use. It provides one output channel that can deliver up to 27 W of power.

Figure 1: The pin assignments of the AP33771 sink controller. (Image source: Diodes Incorporated)

The AP33772 (Figure 2) is a USB PD 3.0 controller that utilizes an I²C interface and built-in firmware to negotiate power and voltage. This provides designers with greater flexibility to implement all PD sink functions. It also offers two output channels that can deliver up to 45 W of power, and has a built-in over-voltage protection (OVP) circuit for each channel which can prevent damage to the device in case of a faulty charger or cable.

Figure 2: Diodes’ AP33772 sink controller comes in the same size packaging as the AP33771, but with different pin assignments. (Image source: Diodes Incorporated)

Diodes also offers a USB PD 3.1 sink controller, the AP33771C, that supports EPR/AVS up to 28 V and Standard Power Range (SPR)/PPS up to 21 V.

Each of these controllers provides low standby power consumption, high efficiency, and thermal protection features. They are available in small footprint W-QFN4040-24 (4 mm x 4 mm) packages, making them suitable for compact and portable devices.

Additionally, Diodes offers two evaluation boards for its USB PD 3.0 controllers. The AP33771-EVB and the AP33772-EVB are both designed for charging applications using a Type-C connector-equipped device and a Type-C connector-equipped PD charger or adaptor. The AP33771-EVB uses a simple resistor setting for USB-PD negotiation, while the AP33772-EVB uses I²C.

Conclusion

USB Type-C is on its way to becoming the global standard for device data connectivity. The USB PD 3.x protocols offer product designers a pathway to create applications that deliver more power, faster charging, and better data transfer for their devices using globally accepted connectors and cables, eliminating the need for device-specific chargers. With Diodes Incorporated's solutions, product designers can readily integrate USB PD 3.0 or PD 3.1 into their devices to enhance performance and improve the user experience.