Author Topic: Missing pin 1 mark  (Read 410 times)

0 Members and 1 Guest are viewing this topic.

Offline Raj

  • Frequent Contributor
  • **
  • Posts: 646
  • Country: in
  • Self taught, experimenter, noob(ish)
Missing pin 1 mark
« on: June 23, 2021, 07:41:14 am »
Did I get a fake from China?
The lm75 I've ordered lacks pin 1 marking
Good thing, I've got a lot of them, so i can burn one of them testing the pinout
I'm guessing, it's the down right one in the picture

The tech drawing of the datasheet clearly shows a pin one mark
« Last Edit: June 23, 2021, 07:48:04 am by Raj »
 

Offline Jeroen3

  • Super Contributor
  • ***
  • Posts: 3634
  • Country: nl
  • Embedded Engineer
    • jeroen3.nl
Re: Missing pin 1 mark
« Reply #1 on: June 23, 2021, 07:55:52 am »
Check if one side of the package may be chamfered. That is the your pin 1 side.
Datasheet also mentions this though, yours must be old.

https://www.nxp.com/docs/en/data-sheet/LM75A.pdf

Also, your screenshot is of the TSSOP8, and it seems you actually have the SO8.
« Last Edit: June 23, 2021, 07:57:37 am by Jeroen3 »
 
The following users thanked this post: Raj

Offline Raj

  • Frequent Contributor
  • **
  • Posts: 646
  • Country: in
  • Self taught, experimenter, noob(ish)
Re: Missing pin 1 mark
« Reply #2 on: June 23, 2021, 08:03:30 am »
yes it is. now there's some doubt gone.
Strange new fangled way of marking pin 1 though.
And indeed... got the package type mixed up while reading the datasheet
« Last Edit: June 23, 2021, 08:06:50 am by Raj »
 

Offline tooki

  • Super Contributor
  • ***
  • Posts: 6571
  • Country: ch
Re: Missing pin 1 mark
« Reply #3 on: June 23, 2021, 12:40:51 pm »
yes it is. now there's some doubt gone.
Strange new fangled way of marking pin 1 though.
Not newfangled at all. It’s one of the established methods. If anything, one that’s falling out of favor as the packages get thinner, leaving no height to be chamfered.
 
The following users thanked this post: Raj

Offline amyk

  • Super Contributor
  • ***
  • Posts: 7444
Re: Missing pin 1 mark
« Reply #4 on: June 23, 2021, 01:28:02 pm »
With the text in normal orientation I don't think I've ever seen pin 1 on an inline package be anything but the bottom left corner.
 
The following users thanked this post: tooki, Raj

Online gcewing

  • Regular Contributor
  • *
  • Posts: 124
  • Country: nz
Re: Missing pin 1 mark
« Reply #5 on: June 25, 2021, 09:33:49 am »
The chamfer might be designed for detection by machines.
 

Offline tooki

  • Super Contributor
  • ***
  • Posts: 6571
  • Country: ch
Re: Missing pin 1 mark
« Reply #6 on: June 25, 2021, 10:46:32 am »
The chamfer might be designed for detection by machines.
Doubtful. This marking type was never universal enough to serve that purpose. Orientation-sensitive SMD components are always oriented the same way in the reel.
 

Offline redben

  • Contributor
  • Posts: 21
  • Country: ch
Re: Missing pin 1 mark
« Reply #7 on: June 25, 2021, 12:34:29 pm »
Agreed, I have not seen any new components from major manufacturer using this chamfer solution.
 


Share me

Digg  Facebook  SlashDot  Delicious  Technorati  Twitter  Google  Yahoo
Smf