Other Parts Discussed in Thread: TMUXHS4212,
Greetings,
we are encountering a problem with our display driving solution.
We are using the DS90UB949A-Q1 to convert HDMI to FPD-Link III which is then sent to a remote Deserializer connected to a Display. In order to be able to switch between multiple video sources we are using the TMUXHS4212 as shown in the picture below:
Our boards were all tested when they first arrived and worked without any problems. After sitting on the shelve for some time only one of the boards works as intended by being able to still reach the locked status with the remote Deserializer and transmitting video data.
Some other boards will work after repeatedly engaging the "Digital RESET0" of the DS90UB949A-Q1 chip. But even though the picture is being transmitted flawlessly register 0x0C[0] will show that there is no link. Also register 0x5A[7] will show no FPD_LINK_RDY status but 0x5A[6] shows that FPD-Link III is being transmitted.
On the rest of the boards we are sometimes able to reach the state as described above but no picture will be displayed.
The boards were tested with different cables and different displays but to no avail. The hardware design follows the EVM example when it comes to passives like CMC and caps.
My question to you is if you have any idea what could cause this sporadic behaviour, especially after the fact that the boards were initially working fine and there were no changes made to them. Could the mux cause problems in terms of signal integrity even tough we payed careful attention to the correct design of the transmission lines?
If you have any approaches to find the cause of this error i would like to hear from you.
