The TMUX7462F detects overvoltage inputs by comparing the voltage on a source pin (Sx) with the fault supplies (V_FP and V_FN). A signal is considered overvoltage if it exceeds the fault supply voltages by the threshold voltage (V_T).

The switch automatically turns OFF and the source pin becomes high impedance so that only small leakage currents flow through the switch when an overvoltage is detected. The drain pin (Dx) behavior can be adjusted by controlling the drain response (DR) pin in the following ways:

1. DR pin floating or driven above V_IH:

   If the DR pin is driven about VIH level of the pin, then the drain pin becomes high impedance (Hi-Z) upon overvoltage fault.

2. DR driven below V_IL:

   If the DR pin is driven below VIL level of the pin, then the drain pin (Dx) is pulled to the supply that was exceeded. For example, if the source voltage exceeds V_FP, then the drain output is pulled to V_FP. If the source voltage exceeds V_FN, then the drain output is pulled to V_FN. The pull-up impedance is approximately 40 kΩ, and as a result, the drain current is limited to roughly 1 mA during a shorted load (to GND) condition.

Figure 9-3 shows a detailed view of the how the DR pin controls the output state of the drain pin under a fault scenario.

Figure 8-1 Detailed Functional Diagram

V_FP and V_FN are required fault supplies that set the level at which the overvoltage protection is engaged. V_FP can be supplied from 3 V to V_DD, while the V_FN can be supplied from V_SS to 0 V. If the fault supplies are not available in the system, then the V_FP pin must be connected to V_DD, while the V_FN pin must be connected to V_SS. In this case, the overvoltage protection then engages at the primary supply voltages V_DD and V_SS.