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ADV7513 HDCP 1080p Issue Flickering Static Snow and Loss of Signal

Question asked by BCK on Feb 2, 2018
Latest reply on Mar 8, 2018 by GuenterL

Hi,  

 

I'm experiencing issues with ADV7513. Our project is in pre-production and it has been suspended,  we have 10 prototypes and 20 products. We haven't seen this on prototypes, but almost 50% pre-products have this issue.

I'm running out of tricks and hoping someone can shed some light on this problem.

 

With HMDI mode, HDCP on, Audio on or i2s clocking, the DELL S2240T will be flickering static snow every few seconds. As long as I turn off the i2s LRCK or SCLK, the screen will back to normal and stop flickering. 

 

0x0C [5:2] = 0000b has nothing to do with stopping flickering, despite all four I2S are Disabled, as long as the LRCK and SCLK are clocking, the screen will start flickering. Meanwhile, if I2S is Enabled, the normal sound mix with popping noise that may be heard.

Flickering static snow

I have connected the output to an HDMI 1.4 protocol analyzer VA-1831, HDCP, HDMI, EDID, DDC, and AUDIO are all green, there is no error reported and no flickering, the CTS, N, and other registers are set correctly.

 

I have opened up S2240T to see what's inside, this model is using a Mstar LCD controller, there are 4 pairs of 0-ohm resistors on the HDMI bus between the connector and the LCD controller to damp the signal. I have probed all TMDS and done an eye diagram, all good and nothing looks too off. 

mstar TSUM098BDC2-3

I have tested on the other 4 sets of the same model S2240T,  I can reproduce the same issues on all of them, as long as the I2S is clocking, the monitor will start flickering static snow every few seconds.

 

We have confirmed that all the signals go into ADV7513 such as 24bit-RGB HS VS DE meets the requirement on the datasheet. (Please refer to the attachments)

 

When the flickering happens, I have also dynamically shifted the Pixel CLK from 0 to 360 degrees, to verify if it is caused by phase shift. Well, it's not.

 

I thought it was due to faulty ESD protection and common mode chokes sat on TMDS pairs, so I removed them all,  and it still flickering.

ADV7513 filter layout

I spray QRA-S481 on ADV7513 to cool it down to -10°C then heat it up to 85°C, it still flickering.  So the temperature is irrelevant.

 

I bend the board around ADV7513 with heavy force, it stops flicking, but the X-ray tells us that all the soldering are properly done.

ADV7513 X-RAY

I can only reproduce this kind of problem with prototypes by combination of a specific weak cable + I2S clocking + HDCP + DELL S2240T

 

The prototypes are using ADV7513 Lot 3483418.1 #1619.

The products are using ADV7513 Lot 3882312.1 #1725 and Lot 3797027.1 #1713.

 

I have a bad product board it issues flicking static snow to all kind of monitors, I have confirmed that the RGB HS VS DE timing is good. Stop the I2S also stops flicking, then I put a Lot 3483418.1 #1619 to replace Lot 3797027.1 #1713. on the bad product board, the problem seems to get fixed.

 

Thanks, 

Best Regards

Ben

 

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Update: 

We have found some pre-product still had flicking problems after tied I2S to LOW.

So we have to force the ADV7513 working at DVI mode 0xAF[1], it seems to be OK by now, but completely lost all audio functions.

 

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SUMMARY

There are several Causal Factors:

HDCP must be ON

HDMI mode must be set

I2S must be clocking

S2240T must be at the end.

1080p must be selected.

 

Sure things:

80% reproducible.

No HDCP Errors when flickering.

Timing requirements are all satisfied.

Eye diagrams are good.

Not due to faulty filters.

Temperature is irrelevant.

X-Ray reveals perfect soldering.

prototypes vs products same PCB design but different makers.

TMDS channel has been carefully impedance matched.

Requesting datasheet, but haven't heard a word from mstar yet.

 

Not Sure:

Better Lot 3483418.1 #1619.

Worse Lot 3797027.1 #1713.

No idea Lot 3882312.1 #1725.

Bend the board seems to fix.

 

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We have tested on a couple of monitors,  most of them work well, except S2240T.

 

here is the list.

 

ASTRO               VA-1831 HDMI 1.4 protocol analyzer

DELL                   S2240T 

GREEN-HOUSE GH-LCT22B-BK

IIYAMA                PL2451MT, E2380HSD

PHILIPS              243V

ASUS                  VT207N, VS24A

MITSUBISHI       RDT234WLM-D

LG                       23ET63V

SAMSUNG         740BX   (HDCP not supported.)

NEC                    AS191WM

ACER                 V195HQL

 

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Here is the timing at 1080p 148.5MHz.

Yellow: CLK, Green: D0

FHD_D0_Timing

Yellow: CLK, Green: D23

FHD_D23_Timing

Yellow: CLK, Green: DE

FHD_H_Timing

Yellow: CLK, Green: HS

FHD_DE_Timing

Yellow: CLK, Green: VS

FHD_VS_Timing

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