Hi,
We have a design in which there are two SN65MLVD204B's on two distant modules, Module A and Module B, that communicate over a differential cable. The cable can be disconnected which disconnects the communication link and removes power and ground reference from Module B.
Module A is powered up at all times and may drive the SN65MLVD204B's DE (Driver Enable) pin at any time, even if Module B is disconnected.
Module B can be connected at any time, including when Module A is driving the differential pair or is tri-stating the differential pair.
When Module B is connected to the cable, the SN65MLVD204B VCC power rail will take ~100ms to power up. During that time SN65MLVD204B on Module B will have VCC=0V and the differential pair is either being actively driven by the SN65MLVD204B on Module A or is tri-stated and possibly floating to up to 2.4VDC
Would TI recommend adding protection against over-voltage conditions, such as diodes from the differential pair (A,B signals) to VCC?
Would ensuring that the Module A and Module B DE (Drive Enable) signals are de-asserted help minimize risk?
These questions arise because we damaged one of the SN65MLVD204B devices on a system and the damage likely occurred during the process when Module A and Module B were connected.
Thanks!
Terry