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AD5755: Thermal resistance value of AD5755

What is the value of thermal resistance theta JC(Junction-to-Case).
Theta JA(Junction-to-Ambient) is shown at the data sheet. But theta JC is not


For the 64 LFCSP 9x9x0.85mm package, I see a number of ~0.2°C/W for Psi Jt.
This is a calculated/simulated number based on a JEDEC 4 layer test board.

JC is Junction to Case, JA is Junction to Air.

We've specified Theta JA on the datasheet with a value of 20degree/W.
Again this is specified for the package with the paddle soldered as recommended.

Theta JC would be lower than this.  Psi-Jt is a calculation of the silicon to
package case differential when mounted on a PCB. This is a more accurate method
than Theta-Jc for the customer to determine the temperature of the silicon (by
measuring the package surface), as Theta-Jc is measured using infinite heat
sinks and no PCB.