Almost no programming required! This PD controller allows you to quickly achieve 100W USB PD power!

Article Overview

This article outlines the core requirements of a PD system. It then introduces Onsemi 's FUSB5101MNTWG PD controller and demonstrates how to quickly configure the pre-programmed controller firmware using an evaluation board, development software, programming / debugging adapter, and PD protocol analyzer.

With the increasing prevalence of Universal Serial Bus Type-C ( USB -C) ports, many users rely on these ports to provide higher levels of power to various connected devices. However, the USB -C specification limits the basic power supply of " Type-C only " devices to a maximum of 15 W ( 5 V , 3 A ).

To overcome this limitation, designers can add USB power delivery ( PD ) functionality and build a Type-C PD device that can deliver up to 100 W (20 V, 5 A) of power within the standard power range (SPR) . Now, developers no longer need to painstakingly program for the full range of USB PD protocols; instead, they can easily configure off-the-shelf PD controllers and add custom and optimized PD functionality to AC/DC chargers and current-controlled USB ports.

Switching converter with protocol-controlled power regulation

Once upon a time, wall-mounted analog chargers for battery-powered devices consisted of only two components: a transformer and a rectifier. Now, meeting demands for higher energy efficiency, greater flexibility, and continuous miniaturization has made powering even the simplest electronic devices a complex task. Today, microcontroller-based switching converters must negotiate output power dynamically with connected smart loads via sophisticated protocols.

USB PD is such a protocol. In version 3.1 of this protocol, up to 240 W of power line power is coordinated via the Intelligent USB Type-C Electronic Marking Cable Assembly (EMCA) connection cable , while maintaining backward compatibility with older USB standards. However, the control of dynamic PD power transfer through the 24- pin USB-C connector goes far beyond the static control voltage on a traditional four-wire USB interface data line.

USB PD devices can operate as a power source for a downstream-facing port (DFP) , a power consumer (or “powered device”) for an upstream-facing port (UFP) , or in dual-role port (DRP) mode. PD source devices internally switch pull-up resistors to two control lines ( CC1 and CC2 ); PD powered devices identify themselves using internal pull-down resistors.

Both CC lines are used simultaneously to transmit PD information up to 356 bits in length at a clock frequency of 300 kHz (Figure 1 ). The shorter control information coordinates the information flow between the two port partners, while the longer data information is used to negotiate power and control the built-in self-test (BIST) or transmit specific OEM content.

Figure 1 : The dynamic length of the PD information structure can reach 356 bits. (Image source: embedded.com , provided by Cypress Semiconductor )

Power negotiation between PD devices

USB PD 3.0 SPR defines several fixed voltage levels between 5 V and 20 V , and only supports a quiescent power profile of up to 100 W. Utilizing the extended capabilities of the Programmable Power Supply (PPS) , USB powered devices can request voltages between 3 V and 21 V from the USB power supply in real-time increments of 20 mV , as needed .

Therefore, PPS simplifies the switching converter electronics in mobile devices, thereby reducing heat loss and accelerating charging speeds through optimized power matching. USB PD 3.1 defines an extended power range (EPR) of up to 240 W and uses an adjustable voltage supply (AVS) to regulate the bus voltage in a higher range between 15 V and 48 V.

Since 3 A exceeds the current-carrying capacity of a standard USB cable, EMCA- specific cables must be used according to the USB Implementers Forum ( USB -IF) guidelines . These cables are characterized by larger conductor cross-sections and thicker insulation. The E-Marker chip in the cable connector verifies the functionality of these enhanced cables via the PD protocol. Thus, these chips influence power negotiation between the source and receiving devices.

PD communication uses special K- codes to describe information. The special K- code sequence that indicates the start of a sequence is called the Start of Packet Code (SOP) . Three sequences are defined in the special K- code: SOP , SOP' , and SOP'' , so that a DFP (such as a PD network charging adapter) can act as an initiator to communicate with either of the two E-Marker chips in the EMCA cable connector , or with a UFP ( USB power jack).

The flowchart in Figure 2 shows the information exchange during a successful power negotiation between two PD devices connected via an EMCA cable.

Figure 2 : Two USB PD devices successfully negotiate power via an EMCA cable. Note: Rqt = Request; Ack = Acknowledge. (Image source: embedded.com , provided by Cypress Semiconductor )

Replace programs with configuration

The complexity of the PD protocol presents developers with a significant programming challenge. A faster approach is to configure a pre-programmed USB PD controller with custom functionality. An example of such a controller is Onsemi 's F USB 15101MNTWG . This is a highly integrated USB PD 3.1 controller that can control the primary-side switching regulator of an AC/DC adapter via an optocoupler, or directly control the DC/DC port current regulator.

This all-in-one solution minimizes circuit complexity by optimizing hardware peripherals, including digital-to-analog and analog-to-digital converters , an NTC temperature sensor, and an NMOS gate driver . Open-source firmware with an application programming interface (API) and an Eclipse -based integrated development environment (IDE) facilitate programming.

Figure 3 : In this USB PD wall charger solution, the F USB 15101 controls the NCP1345 QR flyback switching regulator on the primary side of the AC/DC switching power supply via an optocoupler . (Image source: Onsemi )

Programmers can use Onsemi 's NCP1342 PD 65WGEVB evaluation board (as shown in Figure 4 ) to launch their USB PD power applications.

Figure 4 : Programmers can start working immediately using the NCP1342 PD 65WGEVB USB -C PD 3.0 wall charger evaluation board. (Image source: Onsemi )

The circuit board's storage choke consists of a compact RM8 transformer, providing 60 W (20 V/3 A) of output power. The NCP1342BMDCDD1R2G quasi-resonant flyback switching regulator operates from 9 V to 28 V using only an auxiliary winding . This device is suitable for developing high-performance offline power converters and USB PD adapters, featuring fast frequency foldback (RFF) for improved efficiency across the entire load range. Integrated active X2 discharge capacitors eliminate the need for a discharge resistor and enable no-load power dissipation below 40 mW .

Application 2 : DC/DC current controller for USB PD ports

In this application, the F USB 15101 USB PD controller drives the NCV81599MWTXG four-stage buck / boost and boost / buck DC/DC converter controller. This allows the USB -C port, which originally only outputs 15 W of power , to be expanded into a PD power supply, providing over 60 W of power via the device's internal DC power supply or a battery (Figure 5 ).

Figure 5 : In this DC/DC port current controller application, the F USB 15101 directly controls the four-stage DC/DC converter controller NCV81599 . (Image source: Onsemi )

By using the FUSB3307MPX-PPS-GEVB evaluation board, developers can save time and immediately begin testing and programming with the NCV81599 . This DC/DC current regulator circuit converts the USB port into a PD 3.0 PPS current source, providing up to 5 A of current output from a bus voltage of 3.3 V to 21 V (Figure 6 ). The circuit can detect E-Marker cables and can operate independently or be connected to test equipment.

Figure 6 : The F USB 3307MPX-PPS-GEVB is an evaluation board for the NCV81599 , which can convert USB ports into PD 3.0 PPS power. (Image source: Onsemi )

A DC power supply or battery provides 4.5 V to 32 V voltage to the VBAT input of the F USB 3307 board . The circuit is compatible with constant voltage (CV) or constant current (CC) specifications and features overvoltage, undervoltage, short circuit, overheat, and cable fault protection.

Programming the F USB 15101

The F USB 15010 firmware is a highly optimized Type-C PD controller driver that supports the integrated Arm Cortex M0+ processor. This firmware offers flexible handling of new PD information and additional Type-C state streams. The code is organized in a modular fashion, separating application source code, hardware abstraction layer, platform-specific code, and core USB Type-C PD functionality.

PD core functionality can be configured via project build options or by modifying the vendor information file "vif_info.h" . The codebase includes an Eclipse sample project that can be compiled using an IDE , thus speeding up the evaluation of the Type-C PD standalone controller.

Table 1 outlines the PD profiles supported by the F USB 15101 ; PD O is the Power Delivery Object.

Table 1 : This table shows the PD profiles supported by the F USB 15101. (Source: Onsemi )

Current PDO value:

#define PORT_A_SRC_PDO_VOLTAGE_4 400 // 20000 mV

#define PORT_A_SRC_PDO_MAX_CURRENT_4 300 // 3.00 A

New PDO value:

#define PORT_A_SRC_PDO_VOLTAGE_4 400 // 20000 mV

#define PORT_A_SRC_PDO_MAX_CURRENT_4 325 // 3.25 A

For more details and instructions on installing the IDE , as well as firmware import and binary compilation, please refer to the FUSB15101EVBSPG guide.

The UM70086-D user manual describes the installation of the programming tools and the operation procedures for the one-time flash memory. Segger Microcontroller Systems ' 8.08.91 J-LINK EDU MINI is a suitable Arm Cortex-M programming and debugging adapter that facilitates development work.

Check PD communication

To verify communication between two USB PD devices, developers can use Infineon Technologies ' CY4500 Protocol Analyzer, which supports both USB PD 3.0 and USB -C specifications. This analyzer performs non-invasive testing and accurately captures protocol information on the CC line. The associated EZ- PD analysis software provides a detailed breakdown of all communication between the two USB PD devices and an EMCA cable (Figure 7 ).

Figure 7 : EZ- PD analysis software traces the conversation between two USB PD devices via the CC line. (Image credit: Infineon Technologies )

Conclusion

While understanding the fundamentals of the USB PD protocol is crucial for designing power solutions to meet the ever-increasing power demands of end-user devices, it is a complex protocol that can require significant programming work. To save time, developers can use pre-programmed, highly integrated USB PD controllers to boost the power of USB -C from 15W to over 100W . Customized PD functionality can be enhanced for AC/DC USB chargers and DC/DC USB ports simply by configuring the PD controller . Evaluation boards and PD protocol analyzers can facilitate the development process. Feel free to leave a comment and share your thoughts with the DigiKey team!