Thermal Resistance of L6201PS on FR4 PCB ?

[takumi]

I am writing to inquire about the thermal resistance of the L6201PS. The datasheet provides information on the thermal resistance for an aluminum PCB, but I need to know the thermal resistance when using a glass epoxy (FR4) PCB.

Could you please provide the thermal resistance values for the L6201PS on an FR4 PCB?

Thank you for your assistance.

[Peter BENSCH]

Welcome @takumi, to the community!

the is 

The L6201PS came onto the market before 2003, the data sheet was last updated in 2010. The thermal resistance for the L6201PS was measured at the time on an aluminium substrate because its thermal conductivity was high enough. With FR4, however, some thermal conductivity is only achieved with copper layers, although I am not aware of any standardised procedure. The total power dissipation of 20W stated for L6201PS in the Absolute Max Ratings is also difficult to achieve with a simple board based on FR4.

Sorry not being able to give a more pleasant answer.

Regards
/Peter

[takumi]

Thank you for your response. By the way, is it problematic to design the L6201PS with the same thermal resistance as the L6201?

[Peter BENSCH]

In the case of the L6201PS in the package PowerSO20, Rthjcase, which indicates the thermal resistance from chip to metal slug on the underside, should be of particular interest. Unfortunately it is missing from the data sheet, but comparable devices in the same package with comparable technology have around 2K/W.

If you assume +10%, i.e. 2.2K/W to be on the safe side and know the power dissipation in your application, you can use this to calculate the resulting temperature difference between the internal chip and the metal slug. Of course, the thermal resistance of your board with the (hopefully) thermal vias must be added to the total thermal resistance.

Hope that helps?

Regards
/Peter