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Use Eval Kits to Develop and Test USB Type-C™ and USB PD Products in a Controlled Environment

By Steven Keeping

Contributed By Digi-Key's North American Editors

The latest USB connector/cable, power delivery (PD), and protocol specifications (USB Type-C, USB PD 3.0, and USB 3.2, respectively) make the connectors easier to use and boost USB’s data throughput and power delivery capabilities. However, for designers eager to exploit the new specifications, they are finding that implementation has many challenges. In particular, the higher voltage and current support can lead to damage to incompatible peripherals, and overheating of cables, connectors and ports.

What developers unfamiliar with USB Type-C and USB PD need is a way to experiment with the new technologies in a controlled environment with an appropriate software interface. USB silicon vendors have responded by introducing evaluation kits (EKs) with software and boards which include power supplies, USB connections to a PC and the latest generation of USB chips. These EKs allow developers to gain experience with configuring USB Type-C and USB PD using a proven design with a user-friendly interface. The EKs can also be used as a reference design for the developers’ prototypes.

This article will outline the key attributes of the latest USB Type-C specifications and describe some of the complexities of implementation. It will then introduce kits from ON Semiconductor, STMicroelectronics, and Texas Instruments and show how these can be used to safely explore the capabilities of the new USB technologies. The integrated components upon which the evaluation kit and boards are based can then be designed into new products to take advantage of greater performance while saving space and reducing component count.

Why upgrade to the latest USB specifications?

The key reason for updating a product to the latest USB specifications are:

  • Greater convenience: USB Type-C is based on a compact, reversible plug connector that is easier for consumers and better suits the form factor of modern consumer electronics.
  • Higher throughput: USB 3.2 (introduced in 2017 and now absorbing all prior USB 3.x specifications) offers data rates of up 20 gigabits per second (Gbits/s).
  • Higher power: USB PD 3.0 offers up to 100 watts (5 amperes (A) x 20 volts) for rapid charging of tablets and portable computers.

The USB Type-C connector is mandatory for USB 3.2 Gen 2x2, and future versions of the standard will only be compatible with it (and not the Type-A and Type-B connectors). The specification incorporates a 24-pin connector which provides four +5 volt ground pairs, two differential pairs for the USB 2.0 data bus, four pairs for the SuperSpeed data bus, two “sideband use” pins, VCONN +5 volt power for active cables, and channel configuration (CC) pins for cable orientation detection and management of connections. Note that the pins used in a specific application vary depending on the communication protocol employed and power delivery requirements (Figure 1).

Diagram of USB Type-C 24 pin connectorFigure 1: The USB Type-C 24 pin connector is reversible with the CC pins used for cable orientation detection and management of connections. (Image source: Texas Instruments)

A “fully featured” USB Type-C connector and cable can support the fastest USB data rates. For example, with USB Type-C, a designer could opt for USB 3.2 Gen 1 (SuperSpeed 5 Gbits/s), USB 3.2 Gen 2 (SuperSpeed 10 Gbits/s) or USB 3.2 Gen 2x2 (SuperSpeed 20 Gbits/s) protocols. Note that “not fully featured” USB Type-C connector and cable combinations exist which are unable to support features of the latest specification. The rest of this article will consider designs which employ fully featured USB Type-C hardware only.

USB Type-C also allows the designer to take advantage of the highest USB PD voltages and currents available under the USB PD 2.0/3.0 power protocols. From USB PD 2.0, the specification defines four voltage levels at 5, 9, 15, and 20 volts. Also, instead of six fixed levels of the original USB PD standard, the power supplies may support any maximum source output power from 0.5 to 100 watts. Sources supplying more than 15 watts offer voltages of 5 and 9 volts, those supplying more than 27 watts offer 5, 9, and 15 volts, and those supplying more than 45 watts offer 5, 9, 15, and 20 volts. These various combinations of voltage and current are called “Power Profiles.”

While the flexible power levels have many advantages, they do add complexity as well as some interesting design challenges due to the higher voltages and currents supported by the technology. For example, USB PD requires an additional component—a port controller—to negotiate and implement USB PD power profiles. Designers used to USB Type-A design will not be immediately familiar with these differences, which increases the risk of non-optimal or possibly damaging design decisions.

For example, a USB Type-C system with USB PD can connect to a USB Type-A port through an A-to-C cable; the USB Type-A port VBUS is held at about 5 volts, but the USB Type-C port with USB PD can supply up to 20 volts at 5 A. The port with the higher VBUS voltage drives current into the other port, and many USB Type-A port power switches do not have reverse current protection so they can be damaged by the higher voltage. (For more on USB Type-C and USB PD design, see Digi-Key article, “Designing in USB Type-C and Using Power Delivery for Rapid Charging”.)

Managing USB Type-C complexity

The versatility offered by USB Type-C and USB PD is realized through configurable cables, ports and power settings. USB Type-C connectors electronically detect and configure connections using the CC. USB Type-C ports can be host-only, device-only (functioning in traditional USB host and device roles) or dual-role ports (DRP); the host being the downward facing port (DFP) and the device the upward facing port (UFP).

Other advantages of USB Type-C include:

  • Reconfigurability of dual-role ports. For example, a portable computer may function as a UFP when being charged by a monitor or a DFP when powering a mini-fan.
  • The ability to electronically determine if VBUS is using USB Type-C standard power or USB PD, configuring VCONN if needed.
  • Support of optional alternate and accessory modes.

Port controllers work with PD controllers to negotiate power requirements and direction so that, for example, a device with a modest battery like a smartphone doesn’t try to power a device with high power requirements like a portable computer. Port controllers often include an embedded microcontroller which eliminates the need for an external device to supervise power transactions.

To help manage complexity and ensure a successful design, USB chip suppliers have introduced evaluation kits which allow the designer to experiment with optimized and protected circuitry to evaluate configurations of USB Type-C and USB PD to best suit the application. An example is ON Semiconductor’s STR-USBC-4PORT-200W-EVK, a USB Type-C four port, 200 watt EK. This kit allows a developer to explore the capabilities of USB PD 3.0 at voltage outputs of 5, 9, 15, and 20 volts and currents of up to 5 amps, for a maximum per port output power of 100 watts. Due to limitations of the power supply, the EK is restricted to a total maximum output power of 200 watts across its four ports.

The STR-USBC-4PORT-200w-EVK comprises a USB PD port controller, a high voltage protection switch, and a step-down (buck) power supply controller. It comes equipped with an AC/DC power supply running from a 90 volt to 265 volt input. Overcurrent and thermal protection are built-in. The EK comes with ON Semiconductor’s Strata software which includes configuration tools to test power profiles, experiment with various fault and foldback features, and monitor system telemetry while supplying connected devices with variable charging loads (Figure 2).

Diagram of ON Semiconductor’s USB Type-C EK (click to enlarge)Figure 2: ON Semiconductor’s USB Type-C EK features a 200 watt AC/DC front end and a four-port USB PD output. (Image source: ON Semiconductor)

The port controller on the EK is ON Semiconductor’s FUSB307B, which is designed to implement a USB Type−C port controller (TCPC) with USB PD capabilities. The chip complies with the USB PD interface specification as a TCPC with a standardized interface for a USB Type-C Port Manager (TCPM) and incorporates USB Type-C detection circuitry enabling manual attach/detach detection. The chip’s time-critical PD functionality is handled autonomously, avoiding the need to use a system microcontroller or TCPM.

For its part, STMicroelectronics offers the STEVAL-ISC004V1 USB PD EK. The EK is a ready-to-use USB PD source, based on the company’s STUSB4710A USB PD controller, that demonstrates how to convert a fixed voltage DC power input into a USB PD variable voltage output. The USB PD Controller communicates over USB Type-C CC to negotiate a given amount of power to an attached device and can handle any connections to a DFP or UFP without microcontroller support.

Texas Instruments (TI) also offers a USB Type-C docking station interface EK, the USB-CTM-MINIDK-EVM (Figure 3). The EK is a reference solution for a USB Type-C dock, including USB PD, audio, USB data, power, and video. The EK supports both source and sink power capabilities over the primary USB Type-C PD port. When powered by an external USB Type-C charger, the dock can source 5 volts at 3 A or 12 to 20 volts at 5 A.

The EK incorporates:

  • TUSB8041: A four-port USB 3.0 hub controller which can provide up to SuperSpeed USB via both DFPs and UFPs.
  • TUSB321: A TCPC for determining port attach and detach, cable orientation and role detection. The chip can be configured as a DFP, UFP or DRP.
  • TPS65982: A USB Type-C controller for USB PD negotiation and power path enabling.

Image of Texas Instruments’ USB-CTM-MINIDK-EVM USB Type-C interface EKFigure 3: TI’s USB-CTM-MINIDK-EVM USB Type-C interface EK is a reference solution for a USB Type-C dock including USB data, USB PD, audio, and video. (Image source: Texas Instruments)

The ON Semiconductor, TI and STMicroelectronics EKs guide an engineer through the process of setting up and configuring a USB Type-C design with USB PD.

Development on the ON Semiconductor EK is conducted through the company’s Strata Developer Studio. To start, developers need to apply an AC voltage to the EK, connect it to the PC via the USB Mini-B cable, log in, and allow the PC to detect the EK and download the relevant content.

The developer can make some basic settings to the system including the maximum system power (from 30 watts to 200 watts), a setting which ensures the total PD “contracts” from the four ports don’t exceed the total power from the AC supply, and an “assured power” setting whereby port 1 always has an allocated amount of power and the other ports share the remaining power between them. There is also a fault protection setting which determines the temperature threshold at which a fault condition should be indicated.

The developer can then experiment with individual port settings including:

  • Max Port Power: Once this is set, no contract will be offered that exceeds the limit
  • Current limit: From 0 to 6 A
  • Cable compensation: To reduce voltage drop at the sink device when sourcing higher currents
  • Advertised Profiles: Once a device is plugged in, a list of profiles that were offered to the sink device will be displayed

The developer can then access a browser which details total input voltage and power to the USB ports, and information on the performance of each port including profile (volts), PD contract (watts), output voltage and power, temperature, and efficiency. The EK can connect to an oscilloscope to show more detailed performance information such as VBUS transitions (Figure 4).

Graph of ON Semiconductor’s USB Type-C EK operating characteristics (click to enlarge)Figure 4: ON Semiconductor’s USB Type-C EK can be connected to an oscilloscope for detailed analysis of the chip’s operating characteristics. (Image source: ON Semiconductor)

The STMicroelectronics EK works in a similar manner to the ON Semiconductor EK. Once connected to a DC source of 22 volts (min) and a peripheral device with a USB Type-C connector, the EK’s onboard USB PD controller’s settings can be read from non-volatile memory via an I2C interface to a PC. The PC interface then allows the developer to reconfigure up to five PD voltage and current outputs, peak currents, and undervoltage and overvoltage lock outs. Once these profiles are set up on the PC they can be programmed into the USB PD controller’s memory and used to power the connected peripheral device.

TI’s EK needs to work in conjunction with the company’s USB Type-C enabler board. The enabler board is connected to a PC with a USB Type-A to USB Type-B cable and a DisplayPort cable; the EK is then connected to the USB Type-C enabler board with a USB Type-C cable. The developer can then experiment with the configuration of the USB 3.0 hub, TCPC and USB Type-C controller directly from the PC.

Conclusion

USB Type-C and USB PD bring consumer convenience, higher throughput and enhanced power delivery for either powering—or charging the batteries of—connected peripheral devices. But the technologies also bring increased complexity, making implementation a challenge for developers familiar only with USB Type-A systems.

As shown, developers unfamiliar with USB Type-C and USB PD can now take advantage of evaluation kits from key USB silicon providers that allow experimentation with the technologies in a controlled manner via friendly user interfaces. The EKs can also be used as a reference design for the developer’s prototypes.

Disclaimer: The opinions, beliefs, and viewpoints expressed by the various authors and/or forum participants on this website do not necessarily reflect the opinions, beliefs, and viewpoints of Digi-Key Electronics or official policies of Digi-Key Electronics.

About this author

Steven Keeping

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Digi-Key's North American Editors