SCDS394A March 2021 – October 2021 TMUX7462F
The TMUX7462F device's normal operation is to provide fault protection for the system while minimizing the control logic signals required to route across the PCB. The device works as a channel protector by allowing the signals to pass when in the valid voltage range, and opening the switch if there is a fault case. A fault protected switch can add extra robustness to the sytem against fault conditions while also reducing the number of components required to interface with the physical input channels.
The application shows two channels of the TMUX7462F connected as analog outputs and two channels connected as analog inputs to the PLC system. The analog input channels utilize the TMUX7462F to protect down stream operational amplifiers that are operating at a lower supply voltage than the multiplexer. The TMUX7462F only has overvoltage protection on the source pins, therefore these pins are connected to the external system connector on the analog output channels. If there is a miswiring or wire short issue on the connectors, the channel protector will open the switch channel to help prevent long term fault conditions from damaging the DAC.
If there is a fault condition, the drain pin of the channels can either be pulled up to the fault supply voltage (VFP and VFN) through a 40 kΩ resistor or be left floating depending on the state of the DR pin. This can be configured to match the system requirements on how to handle a fault condition.