DS90UB949-Q1: Stability Issue link video FPD-LINK III with DS90UB948-Q1

Hi everyone,

We are using:

• DS90UB949TRGCTQ1 serializer
• DS90UB948TNKDRQ1 deserializer
• The link is configured to work on dual-lane
• Cable Dacar 535, HSD to HSD from Rosemberger, with characteristic impedance of 100Ohms

In the past we have had problems with video flickering as the operating temperature increases, but we were not aware of the errata "FPD-Link_DS90Ux949-A-Q1_Errata 1v5" to be applied to the serializer.

Applying the latter, in particular for the points:

• 1. PLL lock range over temperature ramp is limited
• 3. Frequency detection circuit may reset the FPD-Link III PLL during a temperature ramp

The problem was solved.

Now, we have problems with video flickering at room temperature.

During the phenomenon, the LOCK pin does not report any problems (it is HIGH), HDMI clock and Open LDI clock do not evidenced anomalous behaviours and they are stable.

As proof we have eliminated the application of points 1 and 3 of the errata and we have seen that the problem disappears.

We would like to have your support.

Thank you in advantage for your availability and support.

Angelo.