Noise in the DVI Output of ADV7511W

Hi GuenterL,

We have few more details to share regarding the observation.

The complete system block diagram is attached. It is summarized below:

1. There are 2 backplanes in a rack.

2. Backplane 1 has Power circuits and Backplane 2 has 14 Cards.

3. VGA IN and DVI IN is given on front panel of card 14.

4. The Card 14 has FPGA as controller (ALTERA ARRIA V).

5. The DVI OUT from FPGA are connected to Backplane.

6. DVI OUT signals are connected to the DVI monitor through Cables which runs through couple of Circular connector.

7. The schematics of VGA IN/DVI IN and DVI OUT circuits in Card 14 is also attached.

We observe the static sparkling white dots only on certain portion of the monitor.They do not change their positions after restart or reprogram of the system.

The visibility of dots varies with intensity of Primary colors (Red, Green and Blue). With the dark intensity, we observe very less dots. If we reduce the intensity of the color (for example shaded RED color, Shaded green color), more sparkling white dots are observed. Can you suggest us how can we eliminate 100% of dots in all color combinations?

There was a change in the observation when we experimented with the CLOCK signal between FPGA and ADV7511WBSWZ (that is signal FPGA_DVI_OUT1_CLK in schematics).

The number and intensity of dots were reduced when CLOCK INVERSION is performed for clock FPGA_DVI_OUT1_CLK.

We took out the Card 14 from the system and connected to a plane Test JIG that has only DVI OUT connector, Backplane connector and POWER circuits. We gave VGA IN to Front panel of Card 14 and observed DVI OUT from DVI connector of Test Jig. We do not see any dot or noise in this case.

Let us know how this issue can be addressed and improved.

If you suspect on Noise issue at the analog side, then please suggest how it can be removed/reduced using any standard filters

If you suspect on digital side, then what are the possible corrective methods?

Thanks & Regards,

Nanjunda M

Hi GuenterL,

We have few more details to share regarding the observation.

The complete system block diagram is attached. It is summarized below:

1. There are 2 backplanes in a rack.

2. Backplane 1 has Power circuits and Backplane 2 has 14 Cards.

3. VGA IN and DVI IN is given on front panel of card 14.

4. The Card 14 has FPGA as controller (ALTERA ARRIA V).

5. The DVI OUT from FPGA are connected to Backplane.

6. DVI OUT signals are connected to the DVI monitor through Cables which runs through couple of Circular connector.

7. The schematics of VGA IN/DVI IN and DVI OUT circuits in Card 14 is also attached.

We observe the static sparkling white dots only on certain portion of the monitor.They do not change their positions after restart or reprogram of the system.

The visibility of dots varies with intensity of Primary colors (Red, Green and Blue). With the dark intensity, we observe very less dots. If we reduce the intensity of the color (for example shaded RED color, Shaded green color), more sparkling white dots are observed. Can you suggest us how can we eliminate 100% of dots in all color combinations?

There was a change in the observation when we experimented with the CLOCK signal between FPGA and ADV7511WBSWZ (that is signal FPGA_DVI_OUT1_CLK in schematics).

The number and intensity of dots were reduced when CLOCK INVERSION is performed for clock FPGA_DVI_OUT1_CLK.

We took out the Card 14 from the system and connected to a plane Test JIG that has only DVI OUT connector, Backplane connector and POWER circuits. We gave VGA IN to Front panel of Card 14 and observed DVI OUT from DVI connector of Test Jig. We do not see any dot or noise in this case.

Let us know how this issue can be addressed and improved.

If you suspect on Noise issue at the analog side, then please suggest how it can be removed/reduced using any standard filters

If you suspect on digital side, then what are the possible corrective methods?

Thanks & Regards,

Nanjunda M