USB Type-C & PD has open the doors to many new features such as DisplayPort and Thunderbolt, which run as an Alternate Mode on USB Type-C & PD. This means that some devices (docks/dongles) that are intended to be used with DisplayPort and/or Thunderbolt Type-C notebooks can be connected to systems that only support USB Type-C only or connected to a notebook with Type-A only ports with a Type-A to Type-C cable.
This is where the billboarding function comes into play. It allows the user (consumer) to know that the device they have connected is not supported. There are two main methods that can be implemented for supporting billboardig using the built-in end point on the TPS65982.
The first method is mainly used in a DisplayPort supported dongle application where there is generally one Data Port (USB Type-A), one video port (HDMI/VGA/DP), and a source of power (Barrel Jack/Type-C Charging Port). The figure below shows a typical Type-C PD dongle design.
The TPS65982 in a DisplayPort supported dongle can be connected directly to the Type-C plug USB2.0 signals. In normal operation, the USB2.0 signals will be passed through the TPS65982 through the USB_RP_P/N to the USB Type-A port. The figure below shows the USB path from the Type-C plug to the TPS65982 to the USB Type-A connector.
When the dongle is connected to a notebook that does not support DisplayPort, the TPS65982 will close the USB_RP_P/N path and expose the end point. This will allow the TPS65982 in the dongle to billboard to the non DisplayPort notebook that a DisplayPort device was connected. The image below shows the path when connected to a non DisplayPort system.
The figure below shows a docking application that has multiple USB and Video ports. This can also be extended to a monitor or a display application where DisplayPorts signals are connect to the monitor directly.
For a docking application where there is a USB hub for multiple USB ports, the TPS65982 is connected to the one of the USB Hubs DFP Ports in order to maintain USB functionality when connected to a non DisplayPort supported notebook. The figure below show the path when the the endpoint and billboarding function is enabled.
These two methods allow the device designer to have multiple options to implement the billboarding function according to their specific design. The TPS65982 end point and billboarding functionality allows for a quick and easy implementation along with its PD communication, power path control, and SBU mux control. For more information and hands on testing pick up one of our TPS65982 BoosterPacks. Check the link below!
