Post Go back to editing

AD8672 is very easy to be damaged

I already destroy more then 10 pcs AD8672 in my experiment.

I just use it as a low noise unit gain buffer.

Supply voltage are +/-12V

IN+ is connected to the reference output from LM399.
IN- and output is shorted to provide the negative supply voltage of AD5541.

But I found that the IN+ will follow the negative supply voltage ( ie, -12V ) in my PCB.

Can any one give me the advice?

Please supply schematic.

Harry


  • FormerMember
    0 FormerMember

    Tina,

      I don't see anything driving node "VSET"??

    Which one are you burning up?  IC4/IC7/IC8/IC11??

    Harry


  • FormerMember
    0 FormerMember

    Tina,

      That's strange.  I would have suspected IC11.

    The only thing I can think of would be power supply sequencing issues.

    Put a 1k resistor in series with each non-inverting input.

    R37 will probably have to be lower.

    Harry


  • FormerMember
    0 FormerMember

    Tina,

      V minus, then V plus, then the analog inputs.

      Theoretically yes, but I doubt you would see it.

    Harry



  • Hi Tina,

    The node that the output is driving is the ground connections of the DAC. Probably not a good idea to do anything else except tying the AGND and DGND of AD5541 to gnd. Having said that, its likely that you are exceeding the maximum differential input of the opamp because the positive terminal of U4 is near the negative supply while connecting the output (which is tied to the negative input of u4) is probably near ground. Also , the dac is a 5V device; even if you did force agnd and dgnd to be at a lower potential you would fry the dac.

    Martin

  • This question has been assumed as answered either offline via email or with a multi-part answer. This question has now been closed out. If you have an inquiry related to this topic please post a new question in the applicable product forum.

    Thank you,
    EZ Admin