I'm not able to find the thermal resistance (JC,JB) of the CAN ADM3053. Can anyone help me?
And can you tell me how I could find it in future cases?
In the datasheet of the ADM3053 you can only find theta JA.
We only specify Theta Ja for these products (53C/W per absolute maximum ratings table).
An estimate for Theta Jb would be 35 C/W and for Theta Jc, 30 C/W.
In practice, the junction temperature during operation will be very dependent on your board layout (the numbers above are general, and assume a pretty standard 4 layer PCB). For example extra copper and/or vias at the ground pins will allow heat to be better dissipated from the part through those pins to the PCB.