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Maximum Device Junction Temperature for SN74CBTLV3245ARGY and Power Dissipation Rating

Mike Lukie58
Prodigy 20 points
Other Parts Discussed in Thread: TS3A27518E-Q1

Device SN74CBTLV3245ARGY

We are using this device in a high temperature application, so we are using the industrial grade part.

We are trying to conduct a thermal simulation to verify that our application will be okay, but do not know what the maximum permitted junction temperature for this device is. We do not know the rated power dissipation from the RGY package either.  Where can we find this information?

  • 0
    TI__Mastermind 45340 points

    Mike,

    If you look at the abs max table in the datasheet you can see that the max storage temperature of the device is 150 deg C and will not cause any permanent damage.  There are also the maximum current, voltage, and package thermal impedance values listed to calculate the max junction temperature the part can generate with full current passing through the switch.  This e2e post will help explain the calculation. 

     

    I have contacted the engineer for this part to help you with additional questions.

    Thank you,

    Adam

  • 0
    Prodigy 20 points
    Thanks Adam

    So following your procedure gives me:

    (0.128 A per channel)2 x (5 ohm resistance per channel) x 8 channels = 0.6554 W

    Thus maximum Junction Temperature = 85 C + (0.6554 W x 37 C/w) = 109.24 C

    This tells me that at full power in an 85 C environment, I would have a Junction Temperature of 109.24 C.
    Does this mean that I could run more current per channel at a lower operating temperature so long as I did not exceed 109 C Junction Temperature?

    What if I wanted to run the device at lower power, would I be able to operate at a higher ambient > 85C?

    For example
    (0.050 A per channel)2 x (5 ohm resistance per channel) x 8 channels = 0.100 W

    Thus maximum operating temperature = 109.24 - (0.100 W x 37 C/W) = 105.54 C?

    Alternately

    In a 100 C ambient then, (109.24 C-100.00 C) / 37 C/W = 0.2497 W

    Thus the maximum channel current would be = sqrt [(0.2497/8)/5 ohms] = 0.079 A

    Do you agree that these are valid conclusions?

    ...Mike
  • 0 in reply to Mike Lukie58
    TI__Mastermind 45340 points
    Mike,

    1) Your first calculation is saying that if you put the maximum allowable current and voltage on the device the junction temperature will increase 24 deg C above the ambient temperature. You cannot run more current per channel at a lower operating temperature because 109 deg C is not a limiting junction temperature it is just information on how hot the junction will get under max operating specs. The max current you may put through the device is limited to 128mA per channel.

    2) When you operate the device at higher ambient temperatures than 85 deg C the performance in the electrical specifications table will begin to degrade. Some of the specifications effected by increase in ambient temperatures include Ron, ICC, and leakage currents.

    3) Unfortunately we cannot guarantee the electrical specification performance at higher than the 85deg stated ambient temperature for this device. You may try We have other switches with 125 deg ambient temperature ratings like the TS3A27518E-Q1.

    Thank you,
    Adam
  • 0
    TI__Guru 55970 points
    Mike,

    Adding to the conversation , TI specifies the absolute max junction temperature to not exceed 150C beyond which there will be reliability issues.
    Operating Tj can be calculated as per the post suggested.
  • 0 in reply to ShreyasRao
    TI__Guru 55970 points
    Exceeding the abs max condition is not recommended since they are set after extensive analysis . There are also other limitations based on the layout of the die, the bond wire current carrying capability , humidity , etc which will override the junction temp calculation at that point.
    Going above 85C will not cause reliability issues but the electrical parameters will not be guaranteed at that point but going above the abs max values will cause performance and reliability issues.