For an application we produced three prototype boards: two of them mount uC p/n MCIMX6X4EVM10AB, and the third one mounts uC p/n MCIMX6X4AVM08AB. The three boards, except for the different uC part number, are identical and are programmed with the same SW.
The application requires the board to control an LCD display via LVDS and two Ethernet lines.
At specific values of uC junction temperature we observed flickering of the display up to lose completely the image in combination with reduction of Ethernet speed from 500Mbb/s down to 200Mb/s. The failure is systematic although the uC junction temperature at which it occurs is not the same for the three boards (see table below). During the failure the core frequency seems not to be affected but it remains stable. I point out that the failure occurrence depends on uC temperature not on board or environment temperature.
On these boards we measured unexpected values of the power supply generated by PMIC for VDD_ARM_IN and VDD_SOC_IN core power inputs. The measure was performed at room temperature during normal operation of the boards. These values are summarized, in the table of attached file, together with the data previously detailed.
1- Can you give us any hints which let us find out the cause of this failure?
2- Can this failure be related to the value of power supply of VCC_ARM_IN and VCC_SOC_IN?
3- Are the measured values correct?
4- Are these voltages controlled automatically by uC via I2CBUS connected to PMIC?
Thanks in advanced
