The CAN (Controller Area Network) bus is one of the most common types of protocols that is implemented in applications that need robust communications such as in industrial and automotive end equipment. The robustness for this protocol can be attributed to the built-in fault tolerances and reporting that many CAN transceivers have today that enable them to sustain themselves in unforgiving environments. In many instances, the CAN bus is physically wired and run right next to power lines of the application and can be susceptible to a high common mode voltage by a short to battery event or the wiring can be run over long distances causing ground faults. Hence, many CAN transceivers have 2 or 3 times the typical battery voltage (12V battery for automotive, so anywhere between 24V and 36V) as fault tolerance and others even up to 60V or 70V as well to combat these types high common mode voltage scenarios. There are several different ways that a multiplexer can be paired with a CAN application and the multiplexer must constitute the same level of robustness that the paired transceiver can provide to be in a high common mode voltage environment.

The first application here would be termination resistor switching for CAN. Termination resistors in a CAN application are a critical element to the overall CAN system and a multiplexer can elegantly be used to get the desired termination resistance based on which peripheral node is determined to be the termination node. In this instance, there are 3 modular nodes and any one can be switched in or out of the signal chain, needing multiplexers to be able to switch in the appropriate termination resistance based on how many elements are present as shown in Figure 3-4.

Next, there are also applications that call for certain switching between protocols to communicate with downstream devices. In the example below, a multiplexer can be used to switch between the CAN bus or RS485 to use them in parallel, but the multiplexer allows the system to pick which protocol needs to be sent downstream to communicate while the other protocol is used locally as shown in Figure 3-5.

One final type of application that multiplexers can be paired up with the CAN interface is simply using the multiplexer to switch between the nodes in a system and a single transceiver. If parallelism is not required, this is a great solution to being able to expand the functionality of a single CAN transceiver to communicate with several different nodes of a system without the need for individual transceivers for each one as shown in Figure 3-6.

While the previous applications are all different instances of using a multiplexer with a CAN interface, they all must abide by being able to tolerate the same types of high common mode fault conditions that the CAN receivers are subject to. In such applications, fault protected multiplexers are a perfect companion to the CAN transceivers as they have very similar fault protection capabilities and provide fault monitoring as well. In addition, sometimes the CAN transceiver requires operation even during a fault condition. For this scenario, high voltage capable multiplexers are the ideal solution here as they can still pass signals during an event with minimal impact on the signal integrity of the CAN bus.