ISO1211: For isolating/broken wire detection.

Hello Tim, 

Thank you for reaching out. The schematic looks good and should work as is. 

Tim De Bondt said:

As one can see there are plenty of differences between this design and the reference design (https://www.ti.com/lit/ug/tidudi9/tidudi9.pdf?ts=1731486592893).

Please consider out new device, ISOM8610, for the optocoupler block. It will be pin compatible with standard optocouplers. 

Tim De Bondt said:

Unexplained differences: Why no FGND_floating and FGND (SenseGND) seperation, why optocoupler shorting this newly made structure instead of FGND_floating and FGND? This would it make it impossible to create detect broken wires no?

Correct. The wire-break detection feature would not be possible without the opto-emulator connection between the floating-GND and FGND connection. The System Description section explains it as below: 

• "A broken wire detection can be executed using only one additional optical switch for each channel. This design does not need any other adjustments to the circuitry. The optical switch disconnects the field ground of the ISO121x devices for a short time and connects it again afterwards. This results in a pulse at the output pin of the ISO121x depending on the status of the wire—broken or connected. This pulse even works for logic '0' input signals if the input signal is coming from a high-side switch with a pullup resistor."

1) One should be able to detect if two signal inputs are shorted together

• There would be no way to distinguish if two inputs are shorted together.

2) One should be able to detect a short between GND and input

• This can be done in software by monitoring the output and detecting an unchanged output after a certain duration. Unfortunately, a short to ground or VCC would look the same to the device as a valid logic low or high. 

3) One should be able to detect a short between PWR(24V) and input

• Same as above.

Best,
Andrew