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DP83848K vs DP83848I (operating junction temp)

Other Parts Discussed in Thread: DP83848K, DP83848I, TLK106, TLK106L

Hi. I am about to decide between DP83848I and DP83848K and, cost and psb space wise, I prefere to avoid the automotive, EP (or the TK series). Thus I am inclined to the K version. However, the operating environment can easily reach 80-81C and I wonder whether any of these two PHYs has sufficient margin when operating at this Ta.

I read the discussion there about the max. operating junction temperature of the DP83848K. Patrick used the formula:

DP83848K Tj oper.max = 85C + (31.7 C/W * 0.294W) = 94.34C

The assumptions applied there do make sense (and the result is not absolutely satisfactory for my application). However, if these assumptions are also applied to the DP83848I, they lead to the conclusion that DP83848I can tolerate a much higher junction temperature:

DP83848I Tj-oper.max = 85C + (83.6 C/W * 0.267W) = 107.3C

This result is strange since I suspect that the die in the K version is not inferior to that of the I version. So, the question is what are the real maximum operating junction temperatures for the I and K versions.


Thank you in advance