I would like to know thermal resistance of junction to the bottom (θjb) for ADAU1372
The above data is not available in Datasheet. Only find θja and θjc.
Please kindly assist.
Thank you for your inquiry. The specification in our data sheets for the transistor junction to case thermal resistance is, in fact, to the bottom side of the case when the part has a bottom exposed thermal pad. From page 13 of the ADAU1372 Rev 0 data sheet:
"θJA represents the junction-to-ambient thermal resistance; θJCrepresents the junction-to-case thermal resistance. Thermalnumbers are simulated on a 4-layer JEDEC printed circuitboard (PCB) with the exposed pad soldered to the PCB. θJC issimulated at the exposed pad on the bottom of the package."
Thank for your feedback.
In other way, do it mean the junction to case (top) is not simulated in ADAU1372?
Sorry that I am not familiar with the thermal measurement.
Yes, that is correct. The junction to case top resistance is not very useful in practice.
These numbers are thermal resistances (a model of how easily heat flows away from the IC). When a package has an exposed thermal pad that must be soldered to a PCB, a relatively small amount of the heat is transferred directly from the top of the package to the air. Heat most goes through the board. Therefore, we provide thermal resistance numbers to a JEDEC standard board and to the air under those conditions.
Please download our application notes "MT-093: Thermal Design Basics" and "AN-772: A Design and Manufacturing Guide for the Lead Frame Chip Scale Package (LFCSP)." MT-093 has links to design calculators on our web site, and AN-772 provides guidelines for the solder mask and placing thermal vias to the bottom layer to dissipate heat. Following these app notes will give the best results.
If you would like to learn more about how θJA and θJC are derived, search the web for "JEDEC thermal standards." The standards are available for free download.
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