• State Resolved
  • Locked Locked
  • Replies 5 replies
  • Subscribers 83 subscribers
  • Views 549 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

F28069's Junction temperature(Tj) at Maximum operating frequency.

Kummi
Mastermind 6220 points
Other Parts Discussed in Thread: TMS320F28069

Hi,

I would like to know if there is any data(approx) about the device's
Junction Temperature(Tj) when it is operating at Maximum Frequency.

I tried to calculate it through Thermal Model info & Current Consumption info
from TMS320F28069' datasheet.

From the document "SPRA953B"   Tjunction= Tambient+(θja x Power).

Tambient = 25°C (approx)
θja = 42.2°C/W (from datasheet Thermal Characteristics Table 5.8)
Power = 3.3V x 307mA (Maximum current consumption from datasheet Table 5.11)

So Tj=25°C + (42.2°C * 1) = 67°C (approx).

With the above calculation the Junction temperature(Tj) at Max Frequency(90Mhz)
would be around 67°C.

Please let me know if the above calculation is proper?

Regards
Kummi

  • 0
    Guru 192875 points

    Hi Kummi,

    The datasheet has this value:


    Regards,

    Gautam

  • 0 in reply to Gautam Iyer
    Mastermind 6220 points

    Hi Gautam,

    I knew this and as you know we have already discussed about "Temperature Range" in a different post.

    I am not asking for the Temperature Range...
    Want to know the Junction temperature(Tj) @ Maximum operating frequency(90MHz).

    Regards
    Kummi

  • 0 in reply to Kummi
    Mastermind 6220 points
    Any comments?
  • 0
    Prodigy 80 points
    The math and calculation looks right. But the assumptions are mismatched. You use the "worst case max" current, which assumes all the peripherals running all the time, with no core idle time, ever, but an ideal room temp. Even room temp can be 40°C+ in some places in the world. So either, use all "typical" numbers for power and idle to get a typical temp rise, OR use all worst case temp, consumptions, and load/idle percentages to estimate the absolute worst case Tj.

    I'd normally use the highest operating temperature that my product has to sustain, then calculate the temp rise. So if your product needs to sustain 50°C ambient, you're still ok with a 42°C rise. However, if you are in, say a automotive app and need 125°C ambient(or more): well, 125°C + 42°C = 167°C, which is out of spec for all grades of the part.

    The final caveat is that θja depends significantly on package, layout, and airflow, so choose an appropriate safety factor, if you are operating close to Tj max.

    Good luck,
    SPG
  • 0 in reply to SecretProjectGuy
    Mastermind 6220 points
    Hello SPG,

    Thank you very much,
    Your detailed answer cleared our doubt.

    Best Regards
    Kummi