I know what it is in general terms of course. But I mean specifically what does the M7 mean. I certainly can't just go to digikey and order an M7 diode because such a part does not exist. I'm making a rugged arduino clone (using kicad) for my own use and intend to put a fuse or possibly resettable fuse in front of that diode so as it doesn't burn out etc... so I have thought of that.

It appears to indicate that the diode must have a 1000v reverse voltage.

See here for the circuit (see the external power supply circuit): http://arduino.cc/en/uploads/Main/arduino-leonardo-schematic_3b.pdf


1 Answer 1


It's a SMT version of a 1N4007 (1A 1000V PIV). They definitely exist (I have a reel of a similar type kicking around somewhere) and they are very popular in Asia (typically from suppliers that are lesser known in the West).

You can use any 1A rectifier of sufficient voltage rating that comes in a DO-214AC (SMA) package.

enter image description here


I had a look at the schematic- the purpose of that diode on the input is to short out a reverse-polarity input. Diodes are pretty rugged and tend to fail short, so unless the source is something like a car battery or PC power supply, there's a good chance it won't fry the board. 50V rating is more than enough for this part- the NCP1117S is only good for 20V in (abs max).

  • \$\begingroup\$ I have always thought such diodes were used as user-input voltage protection, but with a PIV of 1000V it must be that these are rather for ESD protection. \$\endgroup\$
    – sherrellbc
    Commented Jan 16, 2015 at 15:45
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    \$\begingroup\$ With a PIV of 1000V and an If of 1A, surely these are more power supply rectifiers (a la 1N4007) than anything else. \$\endgroup\$
    – EM Fields
    Commented Jan 16, 2015 at 15:59
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    \$\begingroup\$ @EMFields Yup, and across relay coils. There is little (if any) price premium for higher voltage though, like their 1N400x cousins. As I said in my edit, that one is (shunt) reverse polarity protection. There's no reason to have it rated more than 50V PIV. \$\endgroup\$ Commented Jan 16, 2015 at 16:23
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    \$\begingroup\$ Note that they are relatively slow, with several microseconds reverse recovery time. \$\endgroup\$
    – starblue
    Commented Jan 16, 2015 at 20:17
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    \$\begingroup\$ @starblue Yes, trr is big, like a 1N400x. Presumably the M7 can be pressed into service as a poor man's (or woman's) PIN diode. \$\endgroup\$ Commented Jan 16, 2015 at 20:31

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