3A / 5A SMC diode differences?

[[email protected]]

Hi

I need 4 diodes for a bridge rectifier. I have narrowed it down to this
diode:

www.microdesign.dk/tmp/S5AC-13_Diodes_ds16007.pdf

It has a typical forward voltage of 1.05V at 5A

But this one has almost the same forward voltage at that current but is
rated for 3A max

www.microdesign.dk/tmp/S3J_SMC_3A_GeneralSemi_35087.pdf


What is the difference since the case is the same and the thermal
resistance also?

Thanks

Klaus

 

[Boris Mohar]

Hi

I need 4 diodes for a bridge rectifier. I have narrowed it down to this
diode:

www.microdesign.dk/tmp/S5AC-13_Diodes_ds16007.pdf

It has a typical forward voltage of 1.05V at 5A

But this one has almost the same forward voltage at that current but is
rated for 3A max

www.microdesign.dk/tmp/S3J_SMC_3A_GeneralSemi_35087.pdf


What is the difference since the case is the same and the thermal
resistance also?

Thanks

Klaus

The die is smaller for 3A. Consequently the price should be lower.

 

[John O'Flaherty]

Hi

I need 4 diodes for a bridge rectifier. I have narrowed it down to this
diode:

www.microdesign.dk/tmp/S5AC-13_Diodes_ds16007.pdf

It has a typical forward voltage of 1.05V at 5A

But this one has almost the same forward voltage at that current but is
rated for 3A max

www.microdesign.dk/tmp/S3J_SMC_3A_GeneralSemi_35087.pdf

The second diode isn't rated at the same current as the first. The data
sheet gives the forward voltage at 2.5 A.

 

[Klaus Kragelund]

John O'Flaherty skrev:

The second diode isn't rated at the same current as the first. The data
sheet gives the forward voltage at 2.5 A.
--

Well, yes. But what caught my eye was that the typical curves at 5A is
almost identical and the thermal resistance junction to lead is also
simelar. Since the powerloss then is the same, the junction temperature
should then also be the same.

I would assume (assumptions is the mother of all fuckups), that the
rating would then be identical. Ofcourse it could be an issue of
maximum ratings that have larger spread on the 3Amp version than the 5A
version. The forward voltage I qouted was typical data

Regards

Klaus

 

[John O'Flaherty]

John O'Flaherty skrev:

Well, yes. But what caught my eye was that the typical curves at 5A is
almost identical and the thermal resistance junction to lead is also
simelar. Since the powerloss then is the same, the junction temperature
should then also be the same.

I would assume (assumptions is the mother of all fuckups), that the
rating would then be identical. Ofcourse it could be an issue of
maximum ratings that have larger spread on the 3Amp version than the 5A
version. The forward voltage I qouted was typical data

The 5 A diode shows theta J-T of 10 K / W, while the 3 A unit shows
theta J-L, junction to lead, the same thing, of 13 K / W. That's quite
a bit higher, although not quite 5/3.