OPA548: What is the real "junction to case" Thermal Resistance Rjc value ?

Hello,

It looks like you have identified a problem with the OPA548, 7.4 Thermal Table in the datasheet. The table lists the RθJC(bot) Junction-to-case (bottom) thermal resistance 0.2 °C/W, where it should be 2 °C/W (f > 50 Hz) as listed in the Electrical Characteristics table on page 7.

The RθJC listed in the Electrical Characteristics table is for practical purposes the same as RθJC(bot). Newer thermal tables break the RθJC into two components; from the junction-to-top RθJC(top), and from the junction-to-bottom RθJC(bot) of the package. But for a power op amp such as the OPA548 nearly all of the heat is conducted from the junction to the bottom via that lower thermal resistance path. This assumes that an efficient heat sinking system is employed. A small amount of the junction heat is conducted to the top of the package and then radiated.

I'll make note of the problem with Table 7.4 and we'll need to get it corrected. Thanks for bringing it to our attention.

Regards, Thomas

Precision Amplifiers Applications Engineering