Post Go back to editing

ADAU1962-Pins melting, quick schematic check please?

Category: Hardware
Product Number: ADAU1962

Hi,

Is it possible for someone to check my ADAU1962 circuit please?

I'm at the prototyping stage and the first time I powered up the board, pin 49 (AVDD1) burnt out then basically just melted. I replaced the ic and then pin 25 (VSUPPLY) did the same. Strange behaviour that I've not seen before.

I've verified the 5V and 3.3V power supplies are at the correct voltage, there were no untoward shorts after soldering/prior to start up and I'm certain the part orientation was correct. I've checked the schematic again and can't see any problems but something has to be wrong somewhere and I've no idea what.

I've attached a screenshot of the relevant part of my schematic in the hopes that someone more experienced can see if there's any issues there, or at least verify that it is fine, please.

Many thanks.

  • Hello loggytek,

    I know exactly how you are thinking and feeling,... "What dumb thing did I do?" "What obvious thing am I overlooking?" I have been there and done that before. 

    I looked at the schematic snip you attached and it all looks good. I even checked the pinout carefully. I do not know if you are cap coupling the outputs of the DAC to the OpAmps but even if you shorted them all to ground, the current would be limited and the part might run hot but not blow up. 

    My first question is are you using an ADAU1962 or an ADAU1962A? 

    The "A" version can only take AVDD up to 3.3V so this might very well be the problem. Otherwise they are pin and register compatible. 

    You seem to have everything correctly connected. Is the part that is driving the digital input also running on 3.3V for IOVDD? Again, that probably would not draw enough current to melt the part! 

    Dave T

  • I can't believe it, thank you so much! I'd been using the ADAU1962AWBSTZ, nowhere stocks the non A version and I didn't know there was even a variant so didn't think anything of it, there's a lesson here about checking part numbers properly!

    Could you confirm the status of the non A variant please. Having now looked I see DIgikey have no stock and state "not recommended for new designs", neither Mouser nor anywhere else lists it. It is however listed as 'in production' on the analog.com website.

  • Hello loggytek,

    Great! I am glad my guess was good. Sorry you ran into this issue. 

    I think we are on a path to obsolete the 1962 for some frustrating reason. You can use the ADAU1966 and drop that in. You just shut off the extra channels in the register settings and it will be exactly the same. Same registers and pinout exactly. Just make sure it is not the "A" version with that part number as well! Same issue, only 3.3V AVDD.

    We have been having issues with the website update. It was updated in recent months and there have been a lot of issues and I think someone was fired because of it. I think DigiKey is more correct. I would have to inquire internally to see the real status. I usually use the web site just like you did. For now see if you can find the 1966. Well, I just looked on Digikey and it is out of stock. It is also listed as out of stock on the Analog Devices site as well! I checked using Findchips web site and no luck... This is a popular part and it has been on a silicon node that was very constrained since covid happened but we should be through all that mess!

    How many do you need? 

    Send me a PM and a friend request. Depending on how many you need you can place an order on our website and I might be able to expedite it. No promises but if the order is on our site we may have some options. 

    Dave T

  • Hi Dave, thanks again for your reply and offer for order expedition, much appreciated.

    When you say "I think we are on a path to obsolete the 1962 for some frustrating reason." Does that apply to the ADAU1962A as well or just the non A part? 

    It's not too much hassle for me to move to the 1962A and change the PCB but if the 1962A (and 1966A?) is going obsolete then that wouldn't be a worthwhile endeavor!

  • Hello loggytek,

    No, it is only the Non-"A" version and at the moment I think it is only the 12 channel 1962. We came out with the non-"A" versions first and there was an issue with noise when operating single ended. We were able to fix that with the "A" version but the designers had to limit the AVDD to 3.3V for some reason. They are almost the exact same part but if you end up only using one output of the DAC as a single ended signal you have to use the A version. So I would not worry about moving to the "A" versions. They should still be around for a while. 

    We are in the process of qualifying a new fab to produce these so we have more than one source. We would NOT be doing this if we were going to obsolete these soon. It costs a lot to qualify a new fabrication facility. 

    Dave T

  • OK great, thanks. Will change the boards to use the 3.3V part.