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DAC5675A-SP: Maximum Power Dissipation

Leslie Callum
Prodigy 40 points

Part Number: DAC5675A-SP

what is the absolute maximum power dissipation of this device?

  • 0
    TI__Genius 14540 points
    Per datasheet page 7 DC electrical characteristics, maximum power dissipation is 900mW for -55C to +125C version and 850mW for -55C to +115C version of device.

    Thanks
    Christian
  • 0 in reply to Christian Yots
    Prodigy 40 points
    Using this part in vacuum, the datasheet has theta JC of 0.849 degC/W. 1W of power dissipation would only result in just 1degC temperature rise, so it seems that the part can handle much more than 1W. Also, the data sheet derives the supply currents based on Fclk= 400 MSPS and Fout = 70MHz. There is not a quiescent, no load condition. If i take the values in the data sheet:

    Pdigital = 3.3V * 130ma = 429mW
    Panalog = 3.3V * 148ma = 488mW

    Total = 917W

    if i use the Pd = 900W under the electrical performance characteristics, i have exceeded the this Pd (900W versus 917W). What is the real absolute maximum power dissipation? From here i need to derate absolute maximum power dissipation by 80% to show there is margin.

    Thanks,
    Leslie
  • 0 in reply to Christian Yots
    Prodigy 40 points
    Using this part in vacuum, the datasheet has theta JC of 0.849 degC/W. 1W of power dissipation would only result in just 1degC temperature rise, so it seems that the part can handle much more than 1W. Also, the data sheet derives the supply currents based on Fclk= 400 MSPS and Fout = 70MHz. There is not a quiescent, no load condition. If i take the values in the data sheet:

    Pdigital = 3.3V * 130ma = 429mW
    Panalog = 3.3V * 148ma = 488mW

    Total = 917W

    if i use the Pd = 900W under the electrical performance characteristics, i have exceeded the this Pd (900W versus 917W). What is the real absolute maximum power dissipation? From here i need to derate absolute maximum power dissipation by 80% to show there is margin.

    Thanks,
    Leslie
  • 0 in reply to Leslie Callum
    Prodigy 40 points
    Also our clock is at 50Mhz.
  • 0 in reply to Leslie Callum
    TI__Genius 14540 points
    Hi,

    The maximum specs are based on statistical analysis of empirical data measured with the device in an operational mode with maximum Iout(FS), a clock speed of 400MHz, and an Fout of 70MHz. So while it is true the digital power dissipation will never exceed 429mW and the analog power dissipation will never exceed 488mW, it is also true that no device will be considered a good unit if the sum of these two powers exceeds 900mW, meaning that one, or both, of these powers, digital and analog, will be less than the maximum spec.

    The maximum power consumption (900mW) is a characteristic of the device which was determined through simulations and measurements-there is no way to push this value higher or lower as is what you seemed to imply in saying "so it seems the part can handle much more the 1W". Maximum power rating is not a design constraint for this device and is not reported in the datasheet. Maximum power dissipation is reported in the datasheet.

    I'm not sure it makes sense to derate the power dissipation of the device by 20% as this would require a max case temperature of about 25C. Perhaps it makes more sense to derate the maximum operating temperature of the device.

    Let me know if further discussion is required which we can take offline with our quality expert included.

    Thanks
    Christian