When evaluating the safety and reliability of an automotive grade multiplexer, it is important to note their performance under various operating conditions. In the case of TMUX13xxA-Q1, we examine its response to various short-to-battery conditions to provide insight on system level design for automotive optimization. It is important to design around short-to-battery as failure to do so can result in operational issues. The following section shows a deep dive into three scenarios to demonstrate the behavior of the TMUX1308A-Q1 under short-to-battery conditions using a 5V supply voltage.

We begin with the following setup to explore our first scenario with channel S7 selected and channel S0 experiencing a short-to-battery condition.

Figure 9-2 Channel S7 Selected, Channel S0 Experiencing a Short-to-Battery Condition

Table 9-2 indicates values of ∆V_OUT, V_SBAT and minimum R_LIM for various V_BAT cases when considering a maximum allotment of 25mAfor I_S/I_D. Choosing too large of an R_LIM will negatively affect ∆V_OUT as well as substantially limit current flow. Choosing too small of an R_LIM can damage the device.

Figure 9-3 All Unselected Channels Experiencing a Short-to-Battery Condition

We then evaluate the scenario of seeing a short-to-battery condition on all unselected channels at the same time. The follwing table indicates values when considering a maximum allotment of 12.5mA for I_S/I_D(for more information, see Section 6.1). If you have the potential to see short-to-battery on all channels at the same time, then 12.5mA is the limiting factor. Here again choosing too large of an R_LIM will negatively affect ∆V_OUT as well as substantially limit current flow.

Figure 9-4 Short-to-Battery Condition Only on a Single Selected Channel

Evaluate the scenario of a short-to-battery occurring when the switch is closed using a 5V supply. As such, input voltage needs to be limited to 6V. The folloqinf table indicates values of R_LIM needed to keep the voltage of a selected channel under 6V using a standard 5V V_DDfor all short-to-battery cases (for more information, see Section 6.1). Choosing too large of an R_LIM will negatively affect ∆V_OUT as well as substantially limit current flow.

In conclusion, several short-to-battery case studies were observed using a 5V supply. Note that if using a lower supply voltage, the R_Lim values will change for optimal current flow. It is important to protect against short-to-battery conditions as a failure to do so can result in system level issues. Take care to design around these conditions and the electrical characteristics for proper device operation.