1

I'm trying to find an unambiguous way of finding first pin of the tps61220. This is the chip I've experienced the issue with, but am hoping that the answer could contain an approach applicable for similar ICs.

The IC is a few millimeters in length so I couldn't take a picture of it. Here is a drawing that points all the visible artifacts:

enter image description here

The packaging in the datasheet is presented below:

enter image description here

There is no notion about the vertical line in the datasheet, and just looking at it, it can point to two different orientations for pin 1.

However, it seems that the key on finding the pin one is in the way the IC arrives packed in the reel. The below image shows an opposite reasoning for where pin 1 is as suggested in the comments. The argument with the demo board in HandyHowie answer seems to be the strongest so far.

enter image description here

Questions

  • Is this a standard thing that the orientation can only be determined by having the reel?
  • Is don't take the component out of the reel before marking pin one an advice you would give? :)
TheMeaningfulEngineer
  • 961
  • 3
  • 11
  • 25
  • 1
    How does the line point to 2 different orientations? The package drawing seems pretty clear. – brhans Sep 21 '16 at 12:36
  • 1
    Looking at your drawing, the pin 1 is the bottom left one. Many of TI chips do have only this line, so it's quite common for their chips. Also, see this [link](http://electronics.stackexchange.com/questions/48734/how-do-i-identify-pin-1-on-a-chip-with-no-corner-mark) – Andrejs Gasilovs Sep 21 '16 at 12:39

2 Answers2

2

TPS61220

There is a line going from pin 1 to pin 6 on the package.

HandyHowie
  • 4,030
  • 1
  • 15
  • 22
  • Where at the datasheet is there a line? – TheMeaningfulEngineer Sep 21 '16 at 12:34
  • To the left of the C in CKR in the image in the question. –  Sep 21 '16 at 12:36
  • @Alan It most probably isn't. I've had similar issues with other TI chips (such as the PCA9306DCUR). Very ambiguous, and I cooked a number of chips finding out which way round it goes. – Majenko Sep 21 '16 at 12:36
  • @alan Your right, that line is not in the datasheet, but you can see on the image that it is next to pin 1 and 6. – HandyHowie Sep 21 '16 at 12:40
  • @Alan What is expressed in the datasheet is that there should be an artifact near pin 1. Whether it is a dot or a line that extends all the way through pin 6 isn't relevant, as it still tells you the orientation in a non-ambiguous way (the datasheet shows the pins are numbered counter-clockwise, so you can't swap pins 1 and 6). – dim Sep 21 '16 at 14:08
1

Usually you'd have a small dot or indentation at the pin 1. On some devices these are extremely hard to spot and sometimes you have to hold them with a specific angle to the light to see them.

This case seems a bit different as there is a line and it points to two pins. What you can do is apply some rules which seem to be common practice in industry:

  1. Pins are numbered counter clockwise in top view.
  2. Pin 1 is placed in such a way, that pin 2 is not on a different side of the package.

Apply that to the line and it becomes clear that only one pin can be pin 1. (The bottom left one in your pictures)

Arsenal
  • 17,464
  • 1
  • 32
  • 59