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UCC28C43: what is the exact ambient temp range?

Aki Li
Genius 9735 points
Part Number: UCC28C43

In the datasheet SLUS458G, 7.3 Recommended Operating Conditions shows the operating junction temperature of UCC28C4X is –40~105C. Is it wrong? Should it refer to the ambient temp? 

Customer wants to use a PWM controller to support max 105C ambient temp. Is UCC28C4x a suitable one? Thank you.

  • 0
    TI__Genius 13660 points

    Hi Aki,

    The parameters in the recommended table for the UCC28C43 are measured at junction temperature of 105C. The device is specified with a maximum working junction temperature of 150C. In practice many designs work at 125C without issue. There are several curves in the data sheet that show how the characteristic parameters vary over temperature. You can see how these values will change up to 125C.  You should calculate the operating junction temperature by multiplying the power dissipation of the ic with the thermal resisting from junction to case and adding this to the case temperature.

    An estimation of the chip-junction temperature, TJ, can be obtained from the following equation:
    TJ = TA + ( RθJA × PD )...
    where: TA = ambient temperature for the package ( °C )
    RθJA = junction to ambient thermal resistance ( °C / W )
    PD = power dissipation in package (W)

    The important point is that you do not exceed the 150C limit. If you exceed 150C the reliability of the part will quickly decrease.

    Else, have you looked at the UCC28C43-Q1 series of automotive qualified parts? The UCC28C43-Q1 has a recommended temperature range of -40C to 125C
    www.ti.com/.../ucc28c43-q1.pdf   I think customer can consider this device if they still worry about the high temperature.

    Regards,

    Teng

  • 0 in reply to Teng Feng
    TI__Genius 9735 points

    Dear Teng,

    Thank you for the detailed explanation. I found the below noted in the 7.5 Electrical Characteristics

    "..... TA = –40°C to 105°C for the UCC28C4x and TA = 0°C to 70°C for the UCC38C4x, TJ = TA (unless otherwise noted)."

    Why we address TJ=TA here, which is misunderstanding and not the truth. Customer wants to make sure all the Electrical Characteristics data were given under TA = –40°C to 105°C. Could you please help further confirm it? Thank you.

  • 0 in reply to Aki Li
    TI__Genius 13660 points

    Hi, Aki,

    There is no confusion. If you read carefully the note at the top of the Electrical Characteristics table it states that Tj=TA unless otherwise noted. This is possible when testing the part because the test is carried out very quickly and the part does not heat up.
    In a real application there will be some difference between Tj and TA because some power is dissipated in the part causing the junction to be hotter than the ambient. The amount of power dissipated in the package will depend upon many factors such as the switching frequency the capacitance connected to the OUT pin and the supply voltage. 

    Regards,

    Teng