2 What is Channel Expansion

While briefly touched on in the introduction and abstract – channel expansion is simply the act of adding another, independent, communication transceiver to the end application. At a high-level, channel expansion doesn’t require an SBC; channel expansion just requires an additional transceiver output, but in complex systems this is a non-trivial addition to the control system which require more control pins from the applications host controller.

Figure 2-1 High Level Simplified Generic ECU Setup

Not all applications are able to spare GPIO pins to control a secondary transceiver and designers can face an impasse forcing a redesign. Not only are the MCU GPIO pins limiting in the design; there also may not be enough power regulation to power the additional transceiver. CAN transceivers are powered off of primarily 5V supplies, but sometimes 3.3V CAN can be used and since most of these applications run off of a minimum of 12V inputs there must be some type of power management IC within the node. In many cases, if an SBC is used instead of a stand-alone transceiver, the power management can be done by the SBC itself. That is not the case on every system.

Figure 2-2 High Level Simplified Generic ECU + SBC

TI designers of the TCAN28xx-Q1 and TCAN24xx-Q1 SBC families solved this issue and by implementing a channel expansion feature on these devices so that there is no need for additional control lines. In most channel expansion use cases the power from the SBC is sufficient to power the external transceiver as well, allowing for a simpler more integrated power tree. A high-level view of a more beneficial channel expansion scheme using TI’s SBCs pushes the control line away from the MCU and into the SBC.

Figure 2-3 High Level Simplified Generic ECU with SBC using Channel Expansion

So, to put this succinctly, channel expansion is the act of adding an additional communication transceiver to the design of the ECU. Channel expansion can be implemented using TI SBCs and a GFO pin. The following section discusses what the GFO pin is and how the pin applies directly to channel expansion applications.