ADV7619 HPA hardware failure

Question

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

FormerMember · Accepted Answer

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.)

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ADV7619 HPA hardware failure