Post Go back to editing

ADV7619 HPA hardware failure

Hi all!

We've a custom hardware using a ADV7619 in prototyping stage where the second board just failed due to HPA not going high. (It was working for some time.) I'd like to find out why that happens. Our schematic followes the reference design (RXA_5V via 1k to HPA_A, RXA_5V and HPA_A directly connected to ADV, HPA connected to external ESD protection). On the dead hardware we found, that HPA does not raise above 1.7V. If we cut the wire between the 1k and HPA, HPA raises (because its not controlled by the ADV anymore) but SDA is kept low.

The register programming does not follow the recommendations yet. We've configured HPA_AUTO_INT_EDID to mode 2 (HPA goes high if EDID is active and after cable detect delay, HDMI reg 0x6C, bits 1 and 2) and disable the DDC/EDID via Repeater reg. 74 bits 0 and 1 while changing the EDID memory.

Does anymore have an idea why HPA does not work in our setup?

Best regards

Pauliman

Parents
  • FormerMember
    0 FormerMember
on Mar 9, 2020 11:49 AM

Normally HPA is pulled to DDC_5V with a 1K resistor at the source and weakly pulled high with a 47K resistor at the sink.  The ADV7619 HPA pin is an open drain pin only.   It's weakly pulled high at the sink to keep the HPA pin from floating when the cable is not connected.

From your description it does appear the HPA pin is damaged.  You would have to run failure analysis on the part to figure out exactly what the failure is. (Contact your local FAE about going down this path.)

What can cause this problem, (just listing the possibilities, not stating this is what happened)

1) Bad or wrong ESD protections

2) Possible power up sequence difference between the source and sink, where the HPA line has voltage applied to it before the sink to source grounds are connected.  This might cause current surges going through strange paths.

3) At one point of the HPA operations it was asked to sink more current than the specs allowed for damaging the HPA open drain FET.

What ESD protection devices are you using?

Reply
  • FormerMember
    0 FormerMember
on Mar 9, 2020 11:49 AM

Normally HPA is pulled to DDC_5V with a 1K resistor at the source and weakly pulled high with a 47K resistor at the sink.  The ADV7619 HPA pin is an open drain pin only.   It's weakly pulled high at the sink to keep the HPA pin from floating when the cable is not connected.

From your description it does appear the HPA pin is damaged.  You would have to run failure analysis on the part to figure out exactly what the failure is. (Contact your local FAE about going down this path.)

What can cause this problem, (just listing the possibilities, not stating this is what happened)

1) Bad or wrong ESD protections

2) Possible power up sequence difference between the source and sink, where the HPA line has voltage applied to it before the sink to source grounds are connected.  This might cause current surges going through strange paths.

3) At one point of the HPA operations it was asked to sink more current than the specs allowed for damaging the HPA open drain FET.

What ESD protection devices are you using?

Children on Mar 11, 2020 11:09 AM in reply to Pauliman

I can't add anything more then what is stated in the data sheet.

Another approach to this is to put a 33 Ohm resistor in series with each of the pins in question.  The 33 Ohms won't interfere with their normal operation but it can reduce any ESD hits or max current dissipations if they occur.  

From my past experience, damage like this is often caused by burning through the gate oxide or damaging the internal ESD protection on the pin.  The only sure way to know is to have the part go through Failure Analysis where we take the lid off and looks at the silicon directly.  

  • Many thanks GuenterL! We'll try the series resistors with our next prototype.