JAJSNE3B march 2022 – july 2023 TMUX7348F , TMUX7349F
PRODMIX
The TMUX7348F and TMUX7349F detect overvoltage inputs by comparing the voltage on a source pin (Sx) with the fault supplies (VFP and VFN). A signal is considered overvoltage if it exceeds the fault supply voltages by the threshold voltage (VT).
When an overvoltage is detected, the switch automatically turns OFF regardless of the logic controls. The source pin becomes high impedance and allows only a small leakage current to flow through the switch and the overvoltage does not appear on the drain. When the overvoltage channel is selected by the logic control, the drain pin (D or Dx) is pulled to the supply that was exceeded. For example, if the source voltage exceeds VFP, then the drain output is pulled to VFP. If the source voltage exceeds VFN, then the drain output is pulled to VFN. 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 9-19 shows a detailed view of how the pullup or down controls the output state of the drain pin under a fault scenario.
VFP and VFN are required fault supplies that set the level at which the overvoltage protection is engaged. VFP can be supplied from 3 V to VDD, while the VFN can be supplied from VSS to 0 V. If the fault supplies are not available in the system, then the VFP pin must be connected to VDD, while the VFN pin must be connected to VSS. In this case, overvoltage protection then engages at the primary supply voltages VDD and VSS.