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DAC5675A thermal pad

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Kazuhiko Hirano
Posted by
on Apr 10 2012 11:55 AM
Intellectual2350 points
Hello,
 
My customer is using DAC5675 for their product design.
But they can get worse THD performance datasheet spec on their PCB.
 
On their board, the thermal pad is not connected to GND.
Could this be a cause of the bad THD performance?
(DAC5675A-SP datasheet states "This pad must be electrically ground potential.".  But DAC5675A datasheet does not state anything about this.)
 
Best regards,
 
K.Hirano
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  • Matt Guibord
    Posted by
    on Apr 10 2012 15:44 PM
    Expert8985 points

    Hirano-san,

    I'm going to check with the designer about what may happen if the thermal pad is not connected to GND.

    What do they have the thermal pad connected to? Is there enough copper to dissipate heat?

    Regards,
    Matt Guibord

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  • Kazuhiko Hirano
    Posted by
    on Apr 16 2012 18:34 PM
    Intellectual2350 points
    Matt,
     
    There is no through hole on their thermal pad.
    And the thermal pad id not connected GND pins.
    The thermal pad is completely isolated and its area is a bit smaller than its DAC5675 package size.
    I think it does not dissipate heat well.
     
    Anyway, did you talk to the designer?
    What was his/her feedback?
     
    Best regards,
     
    K.Hirano
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  • Matt Guibord
    Posted by
    on Apr 17 2012 16:46 PM
    Verified Answer
    Verified by
    Expert8985 points

    Hirano-san,

    I spoke with the designer and he said that the thermal pad is electrically connected to GND. Not grounding the thermal pad could have an impact on THD in two ways, one is by not providing sufficient grounding to the part and and the second is causing the part to heat up.

    We do not have any data to show what happens when the thermal pad is not grounded, so it may be worthwhile looking at their schematic and layout for other issues as well.

    Regards,
    Matt Guibord

    Report Abuse

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