DS90UB914A-Q1: Output image not stable

Hello,

Can you provide some more details about your system and what you are seeing? How is the image not stable, are you seeing visual disruptions or a black screen? Are any errors being reported? What partner serializer is being used here?

Hi Darrah,

Please see this video of the issue. The serializer is DS90UB913. Have not looked into any errors yet.

Hi Darrah,

For some of them, we determined that UB914 is the culprit, for if we change it to a new one, it can fix the issue. Is it possible for us to send you some of these 'bad' IC to analyze? We want to see if they are fake ones or damaged during PCB manufacturing process. We also find that the current is several dozens of mA less compared to boards that can output stable image.

Hello,

Are you able to access the device registers (both the 913 and 914) to determine what errors are being reported? The device's tolerance to errors varies from part to part. It is common for different devices exposed to the same errors and conditions to respond to and potentially recover differently. On the 914 registers 0x1A, 0x1B, and 0x1C would be good to start with, and on the 913 registers 0x0A, 0x0B, 0x0C would be good to check.

Hi Darrah,

Not able to access the registers. Bought a USB2ANY but it stopped working after two weeks and they refused to replace it. 

We just had another finding. If we lower the VDDIO voltage from 3.3v to 3.2v, it can fix the issue. What can we tell from that? Here is the schematic of the board.

Hello,

It is difficult to pinpoint how the device is behaving without register values. Does the SoC have I2C access to read the registers?

Are you referring to the VDDIO of the 913 or 914? The VDDIO signal is intended to be 3.3V but the device operation will not vary within the recommend operating range.  Is there a large amount of noise on the power signals of the 913 and 914? If there is noise then the higher voltage may be resulting in the voltage seen on the pins going outside of the operating range. The decoupling capacitors differ from the recommended values in the data sheet so it is possible the signal is not being filtered properly. You should also verify that the power sequencing listed in section 10.1.2 of the data sheet is followed. An additional test would be to remove the PoC network and use a different local power supply to the serializer and imager, this removes any noise or influence that the PoC network has on the system.