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 TMUX13xx-Q1, we examine it's 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 TMUX1308-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 10-3 Channel S7 selected, Channel S0 experiencing a short-to-battery condition

Table 10-2 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 10-4 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 below table indicates values when considering a maximum allotment of 12.5mA for I_S/I_D. If you have the potential to see short to battery on all channels at the same time, then 12.5 mA 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. Choosing too small of an R_LIM can also damage the device.

Figure 10-5 Short-to-Battery Condition Only on a Single Selected Channel

We then 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 below table indicates values of R_LIM needed to keep the voltage of a selected channel under 6V using a standard 5V V_DD for all short to battery cases. 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 also damage the device.

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. Caution must be observed to design around these conditions and the electrical characteristics of the device such that proper operation of the device is guaranteed.