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DAC8775: Power dissipation at voltage output type

Lucas Ding
Prodigy 320 points
Part Number: DAC8775


Hi Team,

A question in the DAC8775 datasheet that if the power dissipation data in Fig.96 represent the total dissipation?

Customer found that the temp rise is big when enable the buck-boost converter though there's no load at the Vout. In the datasheet, it should be only about 710~730mW for 24V PVDD. But how about the impact if the customer is using the internal reference?

Thanks.

  • 0
    TI__Intellectual 1570 points

    Hello Lucas,

    Enabling the internal reference will increase the power loss by approx 25mW for a 24V supply. when the buck-boost is enabled and used to power the voltage output DAC, the buckboost outputs are automatically set to approx +/- 15.5V hence the increased power consumption even if VOUT is unloaded. 

    The DAC8775 QFN package has a thermal resistance between junction and ambient of 21.7 deg/W hence for 750mW power increase (assuming internal reference), the temperature increases by about 16C. This is likely what the customer experiences. The theta Ja value assumes that the thermal pad has a good connection to a ground plane other wise the thermal resistance could be higher. 

    Can you confirm if the customer has the thermal pad grounded to a solid plane? By how much is the temperature rising approximately?

    Regards,

    Reza

  • 0 in reply to Reza Abdullah
    TI__Intellectual 1570 points

    Hello Lucas,

    Do you have any update on this issue from customer? Thanks.

    Regards,

    Reza