Author Topic: Help understanding SMD identification.  (Read 2357 times)

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Offline OPTopic starter

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Help understanding SMD identification.
« on: January 18, 2015, 08:00:40 am »
I've searched for a while and haven't been able to find a from the grounds up tutorial on chip identification.

The closest thing I've found so far is the SMD codebook, which is completely useless unless you already know the basics of chip identification. For instance, on their introduction page (http://www.marsport.org.uk/smd/codeintro.htm):
"To identify a particular SMD device, first identify the package style and note the ID code printed on the device. Now look up the code in the alphanumeric listing which forms the main part of this book by clicking on the first character shown in the left-hand frame."

To a beginner like myself, those directions don't make sense at all, and it's just stupidly frustrating:
  • Package style? Looking into package styles, I find the keywords: flat chips, SOT chips, DIP, etc. What type of keyword am I looking for exactly?
  • ID code? Which part of the chip number is the ID code?! For instance, I have a chip "FT9819 G1410 4361I". Is the ID code F, 9, 98 FT, G, G1, 4, 43?! I've looked up entries for all of those, and I do not see the chip listed at all.

Can someone please go over a step by step example, or point me towards a better resource?
 

Offline FreddyVictor

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Re: Help understanding SMD identification.
« Reply #1 on: January 18, 2015, 01:38:52 pm »
ok, not really sure if you are simply designing a circuit using smd parts, or if you are trying to determine the exact parts used on an existing board.
If it's the latter, then it's really not straightforward.

A quick starter on smd parts (sorry, couldn't find your part FT9819) :
as an example, an ATmega328P is the general part no, however, this is available in several packages:
ATMEGA328P-PU is DIL (Dual inline 0.1")
ATMEGA328P-AU is smd type TQFP-32 (32 is no of pins)
etc
often, the last additional chars determine the package
smaller parts obviously won't have this or even their part no printed on them

the list of packages is quite extensive and constantly growing.
onsemi have a pdf (link has been removed from their site) with most of the std ones named
common ones are SOT-23 (often used for transistors/diodes/voltage regulators) and SOT23-5 (often for v-regs) and bigger ones SO-8, SO-16, SO-20 etc
be aware that there are often std & wide versions of some of the SO** chips so it pays to check the datasheet of the part in question

 

Offline Richard Crowley

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Re: Help understanding SMD identification.
« Reply #2 on: January 18, 2015, 01:59:13 pm »
Those codes are for the really tiny packages where there isn't enough space to even print the whole part number.
You seem to be describing a chip with full numbering and marking.
Deciphering a chip identity involves both separating the part number from all the other nomenclature, as well as identifying the package and taking major clues from the larger context:  What kind of gadget is it?  What other chips are around it?  And connected to it?  What signals attach to the board?  What kind of input, output, transducers, etc. are associated?  Photos are invaluable if asking for assistance.
 


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