I have an issue with the DP159 instability(?)
- We let the device run using a 2160p60 source and we found it stopped working after 4 - 8 hours
- We measure DC voltage at a few pins
a. Vcm at input and output pins and we found an offset between the + / - pins on some pairs but not all. If input pair Vcm is offset then output Vcm also offset
(Vcm when chip is good ~ 0.8V but can jump to 1.7V or 2.6V in bad mode and the offset between + / - pin ~ 0.3V instead of 0V)
b. Either SDA or SCL or both pulled low: this is true for either DDC or I2C interface. Note that we use DDC in snoop mode
- We observe TMDS pairs on scope
a. If Vcm is offset then TMDS pair is clipped
b. If DDC or I2C interface pulled low then input TMDS present but no output
c. Sometime DP159 stuck at 1080 mode (or not initialized?) and failed to detect 2160p60 signal
- Cycle power the board or unplug / plug back the source do not help resetting the DP159, it is stuck in that unstable mode. Applied voltages = 1.095V / 3.321V
- The MOST interesting thing is that if we take that board and reflow the DP159 then everything seems resetting and the DP159 works OK again (after cooling off the board) for a few hours before getting back to that unstable mode
I have no clue why heating up the chip seems helping. And I have multiple boards behaving as such. Could it be an assembly issue? We make sure that the board is cleaned properly after soldering and no visible residue. Hope someone had experienced the same thing and found a way out.
Thanks
Lam Huynh
