USB Type-C multiport adapters are gaining popularity among business travelers (like me) due to demand for the lightest and thinnest notebooks. These adapters allow the offloading of data (such as USB 2.0), video (such as VGA, HDMI) and power connectors from the notebook, making it possible to reach form factors that otherwise would not be possible. While it is exciting to see the thinner form-factors enabled by the USB Type-C connector, I would like to highlight another interesting feature that USB Power Delivery (PD)-enabled notebooks and adapters can support.
Figure 1 shows how I normally power my notebook on the go using the adapter’s USB Type-C port. In this configuration, the notebook is a sink when charging from the adapter. When I need to project to a monitor, I use one of the several video connectors available on the adapter. Similarly, I connect to an external hard drive via the USB Type-A connector.
Figure 1: Block diagram of an adapter powering a notebook
Thanks to the Quick Swap feature supported by the TPS65982 USB Type-C and PD controller, I do not need to worry about causing a disruption during a customer presentation or interrupting a data transfer when I remove the charger from the adapter. Leveraging the Vendor-Defined Messages (VDMs) introduced by the USB PD protocol, the TPS65982 allows an Alternate Mode where a separate power path on both the notebook side and adapter side can supply power in case the charger is removed.
When the Quick Swap-enabled notebook connects to an adapter, the notebook exchanges USB PD VDMs with the adapter to discover if the adapter is also Quick Swap-enabled. When a Quick Swap-enabled adapter is connected, the notebook enables reverse-current protection for the TPS65982’s internal power path, turns on a 5V supply and sends a USB PD command to enter Alternate Mode. As long as the charger remains connected to the adapter, the internal power path remains switched off and the external power path provides power to the notebook.
When the charger is removed from the adapter at any point, the notebook seamlessly becomes a source and starts providing power to the adapter from its battery through the TPS65982’s internal power path, ensuring an uninterrupted user experience in terms of data and video as shown in Figure 2. When the charger is connected to the adapter again, the internal power path enters reverse-current protection and switches off. The notebook seamlessly stops supplying power to the adapter and switches back to a sink.
Figure 2: Block diagram of a notebook powering an adapter
This is one of many enhanced user experiences enabled by the USB PD standard that allows original device and equipment manufacturers to deliver value add to their end products.
As innovation continues, the TPS65982’s firmware-based implementation offers the fastest time to market for these enhanced user experiences.
Additional resources
- Read the TPS65982 data sheet.
- Read other blog posts about USB Type-C.
- Jump-start design with the TI Designs USB Type-C and USB PD Controller Power Switch and High-Speed Multiplexer Reference Design.
Read TI’s white paper
