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AD8129/AD8130 Power Sequence

So I have an AD8129 in my design, would there be an issue with powering the negative rail for 400mS longer than the positive rail during shut down. Were trying to figure out why they keep dieing on us. We have tried diodes  across inputs with no luck.  We our operating with a gain of 4.6, But stability doesn't seem to be the issue, my theory had been it was oscillating it's self to death but. Nether diodes or higher gain seems to work. Once the amp "Dies" it's noise output sky rockets.  

circuit :

Parents
  • We have tried adding diodes, cranking gain to 11. with no luck. But if we built this amp in Isolation we did find that if we left the negative rail on to long at power down that would create the problem.  so we addressed the 400mS of time that the negative rail remained high at shut down that seemed to ameliorate the problem but not solve it.  Any insight from analog devices, or other users would be appreciated.  

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  • We have tried adding diodes, cranking gain to 11. with no luck. But if we built this amp in Isolation we did find that if we left the negative rail on to long at power down that would create the problem.  so we addressed the 400mS of time that the negative rail remained high at shut down that seemed to ameliorate the problem but not solve it.  Any insight from analog devices, or other users would be appreciated.  

Children
  • Hi Chris,

    I want to apologize for the delay in getting back to you.

    Is it at all possible for you to remove the delay on the negative side to see if the issue goes away?

    If not, can you add a larger cap on the positive side to make the 400ms delay much shorter? 

    That would be my initial attempt to see if that is what is causing the problem. 

    Also, is the part getting hot at all? Is it possible for you to email your full schematic
    to CIC.americas@analog.com so I can take a look at it?

    Thanks

    Charly