Questions about the thermal resistance of C4D40120D

Henry23

Dear support member,

I have a question about the thermal resistance of discrete diodes with TO-247-3 packaging(C4D40120D).

There are two thermal resistances from junction to case shown in the datasheet, i.e., per leg and per device. What is the difference between them?

We connected an anode pin and the cathode pin for the measurement, and which value should we compare to? Per leg or per device?

Looking forward to your answer.

Best Regards

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Forum_Moderator

Thank you for your post, it has been approved and we will respond as soon as possible.

TBhatia

Hello Henry,

Thank you for your question. C4D40120D is 2 diodes in parallel inside a single discrete package. Each Diode has a current rating of 20A @ 150C so the total current rating of the device (one package) is 40A @ 150C.

The two anode pins for each diode are separate but are connected at the cathode at pin 2 and case. Since you're only using one of the anode pins, you're essentially using only one diode of this package and therefore should be looking at all ratings for "per leg" in the datasheet including the thermal impedance.

To utilize the full current capability of the device, you will need to use both diodes and therefore connect both anode pins. Hope this answers your questions!

Henry23

Hello Bhatia,

Thank you for your support. I got it.

Best Regards

Henry