diode polarity
diode polarity
(OP)
Hi, I am using a surface mount diode on a pcb I am designing. I have created the footprint in Altium but I can't figure out which pad is the cathode and anode. Which one is the larger pad?
Here is the datasheet and the digikey link:
http://www.diodes.com/datasheets/ds30516.pdf
http://www.digikey.com/product-detail/en/DFLS240L-7/DFLS240LDICT-ND/700152
Thanks!
Here is the datasheet and the digikey link:
http://www.diodes.com/datasheets/ds30516.pdf
http://www.digikey.com/product-detail/en/DFLS240L-7/DFLS240LDICT-ND/700152
Thanks!





RE: diode polarity
There is a hint in note 1, which seems to indicate that the larger pad is the cathode.
The packaging datasheet mentioned in note 6 is just as useless as the main datasheet - no polarity information given.
RE: diode polarity
See the drawing on p.3 of the datasheet.
Benta.
RE: diode polarity
Except for those diodes where it's a dot, or just two different colors, or it's the package shape (flat side or a notch), or its a 3-pin device, and you are supposed to know that the middle pin is the cathode...etc. I've seen an awful lot of variation in diode packages out there, and I'm just a mechy type.
Every decent data sheet has the polarity/pinout for whatever device specifically called out, to avoid having to determine the polarity by trial-and-error.
RE: diode polarity
Not a fire-proof rule, but something that can be used to verify or falsify a preliminary guess.
Gunnar Englund
www.gke.org
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Half full - Half empty? I don't mind. It's what in it that counts.
RE: diode polarity
My statement was a little broad, I agree.
Benta.
RE: diode polarity
RE: diode polarity
-AK2DM
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"It's the questions that drive us"
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RE: diode polarity
TTFN
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RE: diode polarity
Is there something on pg. 3 that clearly identifies anode or cathode and tells which pin/pad is which? Besides the stripe that benta noted, which I think even he will admit, is not clearly specified as marking the cathode. Yeah, ok, "convention says" the cathode is marked, but those kind of assumptions make guys like me fry little electronic bits. And not just me, either - my EE compatriot had a whole slew of boards built with the diodes reversed, because the packaging drawing was not clear, and he made an ASSumption. Stupid, incomplete or poorly written data sheets should be called such. We nearly missed a shipment because of the screwup.
Sorry, had to vent. I will go back to sleep now.
RE: diode polarity
I remember testing a batch of failed boards that looked like open diodes in a bias circuit. Pulled out one of the 1N4002 diodes and did a quick test with and ohm meter. Conducted one way and not the other. It was then I noticed that the band was painted on the wrong side.
RE: diode polarity
Yes the very bold... clearly visible... black cathode mark on the top view in the "Package Outline Dimensions" section. I wouldn't even think twice about it. That's CLEARLY a cathode marking.
RE: diode polarity
I don't know enough about surface mount diode manufacture to guess whether to expect a similar mis-mark rate or not.
Mike Halloran
Pembroke Pines, FL, USA
RE: diode polarity
Unless it isn't.
RE: diode polarity
RE: diode polarity
Z