I'm just wondering why this schottky diode have three pins? enter image description here

I know two of the pins acts like rectifier but what does the a third pin do?



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    \$\begingroup\$ Take a look at the datasheet... \$\endgroup\$ – stefandz Oct 13 '15 at 12:40
  • \$\begingroup\$ Have a look at the datasheet, pin 2 is floating \$\endgroup\$ – Bimpelrekkie Oct 13 '15 at 12:40
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    \$\begingroup\$ For the diode in question, nothing semicon.panasonic.co.jp/ds4/DB3J208K_E.pdf. It's a reasonable question though why some SMD diodes are packaged like this. That's in fact not too different than the (more general) recent hot question: electronics.stackexchange.com/questions/194693/… \$\endgroup\$ – Fizz Oct 13 '15 at 12:57
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    \$\begingroup\$ @Olin - The datasheet tells that pin 2 is not connected (NC) but doesn't say why the three pin package is used instead of a two pin one. The question isn't dumb nor directly answered in the datasheet at all. \$\endgroup\$ – Ricardo Oct 13 '15 at 13:58
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    \$\begingroup\$ @Ricardo The OP asked what the third pin does, which is answered directly in the datasheet. If he didn't know why some packages have N/C pins, he should have done a little research before asking here. Those answers were also right in front of him. This was a question that could be answered easily if he'd done a little bit of research first. \$\endgroup\$ – DerStrom8 Oct 13 '15 at 14:27

In general, single diodes in 3-lead SM packages have no connection on the third pin. This is a fairly common practice in the industry.

I don't have a solid answer as to 'why' they do this, but will share a few possibilities for debate:

  • You cannot install a single diode in a 3-lead package with reverse polarity because of the asymmetry of the package; if the diode were in an 'inline' 2-lead SM package (like SOD323) there is a chance of reverse installation

  • 3-lead packages are larger, allowing for larger die sizes (better thermal performance), easier installation by pick-and-place machinery (generally, the smaller the part, the trickier installation is) and easier optical inspection


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