Where can i find thermal parameters for ADM3251E?
Theta-ja is quoted on the datasheet as 47.05 degC/W.
There is no Theta-jc parameter specified on the datasheet. It is normally only quoted where all or nearly all of the heat is dissipated through the surface in consideration. As stated in the datasheet, because it is not possible to apply a heat sink to an isolation device, the device primarily depends on heat dissipating into the PCB through the ground pins.
ADI does not usually quote the θjc value for our plastic packages because the case temperature is non-uniform, and therefore the point of measurement can influence the temperature result, leading to incorrect calculation of the junction temperature.
Based on a 20-ld wide body SOIC package with 6 internal die the Theta-jc will be ~15 degC/W.
Please let me know, the absolute value of Tj(max)?
If by Tj(max) you mean the maximum junction temperature for device to still operate within datasheet specification, then it can be calculated by Tj_max=Ta_max+Max_power x Theta_ja
where Ta_max is the max operating ambient temperature, 85degC
Theta_ja= 47.05 degC/W
Max power would be Icc_max x Vcc_max=145mA*5.5V=0.8W
from the above equation the Tj_max is about 122.5 degC.
Thank you very much for your answer.
I understood very clearly.
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