Bought some DMN3042L MOSFETS from Digikey. ID PN is very odd, can you explain?

[TT_Vert]

This s what I ordered https://www.digikey.com/product-detail/en/diodes-incorporated/DMN3042L-7/DMN3042L-7DICT-ND/5223244.  What confused me is the marking on them is 4L E9 (See pic).  Looking this number up anywhere including here: http://www.s-manuals.com/smd the 4L doesn't exist.  So if I was in a situation where I didn't actually know what this is how would I ID it?  Of course the datasheet shows this marking but I would never get to this datasheet if I didn't already know what it was.  So as experts, how wouldyou ID this?  Am I missing something here?  Googling 4L would net me way too many random results to be useful.  In the SMD codebook it only shows 4L as dual series GP RF pin diodes.


Dave

[amspire]

If you look at the datasheet at Digikey, they explain the SMD code.

4L is the product code for the DMN3042L

E9 is the date code: September 2017

[TT_Vert]

I understand what the figures mean.  What I don't understand is how I would find the datasheet to begin with based on those numbers if I didn't already now what I had purchased?  IE 2 years from now if I go into my drawer and see this or if it's in some random circuit down the road and I need to replace it.  Know what I mean?

Dave

[amspire]

You hope in two years the SMD code is on a list. Most products are unfortunately not designed to be serviced.

[TT_Vert]

Well sadly that makes sense.  What do you experienced guys do?  Figure out what it is and do the math to figure out the specs of what you need?

Dave

[T3sl4co1l]

Looking up the code, given the datasheet, is usually easy.  (That is, they usually say what the marking is. But, often they don't...)

Looking up the datasheet, given the code, is not easy.

As with phone numbers and IP addresses, you need a reverse lookup, a searchable database.

These lists do exist (s-manuals is the most complete one out there, I think), but they aren't comprehensive.

What do you do?  Well, there's always the fetal position...

Alternative methods?  If you really need to fix the thing, you can try to reverse engineer the circuit, at least in the immediate area, and see what the part is doing.  Does it have power and ground pins?  Does it have a normal transistor (BJT or MOS) pinout?  Is there an obvious polarity against the surrounding circuit?  Is it in a DC-DC converter?  Logic level input?  Switching output -- LEDs or something else?  Is it surrounded by resistors, part of an amplifier?  What values of capacitors / inductors are nearby, that might hint at parameters (say, an RF type)?

So, it's one of those problems where, if it's not easy, it's very much more difficult...

Tim

[Peeps]

This is a big problem actually when repairing gear. Probably my biggest roadblock to fixing something is deciphering SMD codes. My technique involves measuring the package with calipers to identify it then searching for the smd code + package. In this case that's be 4L sot23. Then go through datasheets and try to match markings and confirm pinouts.
If its in circuit you can always identify ground and a power pin and draw a schematic of the area.

Theres also this smd codebook that has helped me out from time to time. I always check here first before googling. As the description says there's a few hundred thousand markings organized by pin count. http://www.turuta.md

[Nusa]

For stuff in your drawer/stock, make sure you keep something with them that says what they are.

For a mystery item, you can remove it from the circuit and use a transistor tester, which may sufficiently identify it.

[sleemanj]

As components get smaller and smaller, codes are not printed on them at all any more... problem solved!

[TT_Vert]

Thanks guys.  I'll bookmark that reference page.    I better get better at electronics if I want to get to this level of IDing these components.

Dave

[Bud]

What I don't understand is how I would find the datasheet to begin with based on those numbers if I didn't already now what I had purchased?  IE 2 years from now if I go into my drawer and see this

I store SMD parts in their original labeled bags, just may cut the bags with scisors to make them smaller and keep the label.

[TT_Vert]

I may have to do this.  I had 3D printed some nice drawers and they don't really have room for labels and I cannot have a separate drawer for each one off item I have but for now i'll just cut out the info from the invoice and slide it into the drawer face.  Until I run out of drawers   Perhaps you guys have a logical way for organizing the small one off components?

Added a few pics, looks like my pup wanted in on the action.  And call me Fred Flintstone (I think many of you will get this reference)

Dave