AnsweredAssumed Answered

Dead ADV7441A

Question asked by Janos on Jul 25, 2012
Latest reply on Jul 30, 2012 by GuenterL



We have developed a board with ADV7441A. Some of the boards produced by us, have the strange behavior.

The board passed all factory test, but after the delivery the customer reports, that the HDMI input can not lock to the source.

So they have returned the board to us. (There are two of these boards returned, from two different customers, so we have evaluate the problem.)



First of all, the ADV7441A analog part works,  we can nicely use it also on the two "dead" boards. (Component, RGB mode)


But, the HDMI part seems to be broken. Let me describe the results of my evaluation.


From software point of view.

To get lock, we go through certain stages, as described in the datasheet






The module is circulating in stage 1-3... Can not obtain lock. The HS/VS output is crazy... EAV SAV also... Pixel output clock...


All other circumstances are ok.

-Input 0, Port A selected

-Port A Active Clock (!!!)

-Port A Terminated

-Even the input HDMI Freq measurement unit can measure input clock. (!!!)

-I2C EDID is ok.


From hardware point of view.

The TMDS_CLK lines can be easily measured, while it is only the pix clk. (75 MHz current case. 720p )

On a good board, we can see as expected CML differential signals, with a "common mode voltage" roughly 3V.


On a bad board, the CLK_N signal is still ok, but the CLK_P has bad "common mode volatile". See scope image. (SCRN0128.JPG )

The HDMI transmitter (DVB receiver) might recognize this, and makes periodical restart off channel, every 300us or so. (SCRN0127.JPG )


I think it has something wrong with the termination inside the ADV7441A !

Once the board is broken, it never comes to alive again! Power cycles do not help...



The board has switchable power supply rails. (Independent 1.8 and 3.3V, with a SIP4280A switch). So sequencing is ok I think.

We have probable good reset pulse. PGB201 ESD protection on TMDS lines.



Do you have any idea?