“When the automotive industry introduced the concept of’infotainment’, it was a major change for manufacturers because it brought closer integration between automotive functional systems and non-functional systems. Infotainment creates a new interface for drivers, so its impact on how we interact with technology is almost as important as the introduction of mobile phones.

“

When the automotive industry introduced the concept of’infotainment’, it was a major change for manufacturers because it brought closer integration between automotive functional systems and non-functional systems. Infotainment creates a new interface for drivers, so its impact on how we interact with technology is almost as important as the introduction of mobile phones.

We have seen leading standard configuration files and user-upgradable audio systems—most of which are independent and replaced by systems suitable for manufacturers to provide more features. They quickly evolved to include navigation, while gradually integrating more control over other systems in the car, such as climate control. Safety features, the predecessor of today’s advanced driver assistance systems (ADAS), such as reversing cameras, have also become part of the infotainment center. In the same period, these systems have been further expanded, making mobile phones in the car’s growing list of features Indispensable.

Mainly thanks to the USB interface (although Bluetooth also plays an important role), it is now easy to connect your phone to your car to access media, access contact information or just make a call. When you choose to connect via USB wired connection, the additional benefit is that your phone battery is charged by the car when you go to work in the busy morning or drive leisurely in the suburbs.

This convenience should not be underestimated, especially considering that if used frequently, many smart phones are still difficult to maintain a full day on a single charge. But with the development of the USB interface, car owners will expect their cars to evolve as well. The automotive industry does not evolve as fast as the consumer sector, so the introduction of a new connector USB Type C will have a major impact on how automakers can solve this very practical challenge.

They cannot ignore the fact that the connector configuration file is changing. As the frequency of replacement of mobile phones is much higher than that of cars, consumers may accept some lag, but when choosing a new family car, supporting the latest USB interface will undoubtedly be what car owners expect, especially because the new standard will support more types Charge the device. It will no longer be limited to mobile phones, laptops, cameras, tablets and other devices that require higher power, which can all be charged via USB Type-C.

BMC provides keys

The technology that enables the USB connection to provide or draw up to 100 W of power exists in the power supply (PD) part of the specification. It requires a power supply that can provide such a power level, in addition, it also relies on the USB controller to be able to interpret the connected device requirements. Although power supply has always been an important aspect of the USB specification, the use of Type-C connectors and USB 3.x specification cables can best achieve the current higher power levels.

The Type-C connection can be plugged forward and backward, which brings more convenience to users, but makes development more complicated. The direction is managed by a new configuration channel (CC), which has two dedicated pins on the connector and supports the connected devices to negotiate how much power they need to provide or draw. The protocol used by this channel is a differential Manchester code called bi-phase symbol coding (BMC). The USB Implementer Forum (USB-IF) defines five power supply profiles: 10W, 18W, 36W, 60W and 100W. Using the BMC protocol, power configuration files can be exchanged between two devices with USB Type-C interfaces. The coding scheme uses conversion to represent logic levels, not absolute levels, and it combines its own clock signal to make synchronization easier. However, the BMC protocol relies on a physical interface that can reliably decode signals in an electrically challenging environment, and few electrical environments are more challenging than the vehicle environment.

Add Type-C to the car

ON semiconductor’s FUSB302B is a programmable USB Type-C controller that is fully compliant with AEC-Q100 vehicle regulations, includes power transmission, integrates a BMC client configuration channel, and supports version 1.1 of the full Type-C PD 2.0. This means that CC can be used to detect when a device is connected or disconnected, the current function of the host or device, and whether there is an active cable, and to select the required mode (such as audio adapter or debug accessory mode). Figure 1 shows a block diagram of a typical application.

Figure 1: Typical application block diagram

This shows the I2C interface between the controller and the host processor, indicating that FUSB302B does not integrate its own processor. This is an important feature of the device, because it does not need to provide additional power for an integrated processor, while supporting the firmware to reside anywhere in the system, if the USB specification is modified, it will provide manufacturers with a simpler Upgrade path. Figure 2 shows a more detailed application example. FUSB302T is the default source configuration option of FUSB302B and can be used as part of a complete system when implementing USB Type-C in automotive applications.

Figure 2: Application example shows that dual USB ports provide 100 W capability

FUSB302B implements a CC switch that enables it to detect whether it is connected as a device host or a dual-role port, managed by multiple comparators and a programmable DAC controlled by software on the host processor (Figure 3).

Figure 3: Configure channel switch function

By implementing a thin BMC client, including the BMC physical interface (PHY) and packet FIFO, the host processor can use the I2C interface to send and receive data packets. This shows that all functions of the USB BMC PD can be accessed through software, using passwords to read and write the FIFO of FUSB302B. The password is flexible and supports all functions of the USB PD specification, including fast packet processing of burst writes to the FIFO. Every valid data packet received through the CC is stored in the FIFO; the BMC receiver senses the activity on the CC and enables the internal oscillator. Once detected, a dedicated interrupt is used to notify the host processor that a valid data packet has been received. Figure 4 shows the block diagram of the USB BMC PD block.

Figure 4: USB BMC PD block

Flexibility to provide long-term solutions

Through the firmware running on the host processor, the USB controller is almost completely software-defined. It provides a long-term solution for car manufacturers to implement USB PD (USB PD3.0 1.1 version), and to meet any future revisions to the specification through a simple firmware update to the host processor.

The optimized design of FUSB302B combines high performance and low power consumption and is realized through software configuration. By choosing a software-configurable format, it does not require another embedded processor that takes up resources, and increases its flexibility by supporting the definition of its functions by the host processor. This provides automakers with a path from Type A/B to implement USB PD, and finally implement Type-C without changing the USB controller.