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I want to buy an SMD IC. More specifically, this one: https://www.ti.com/product/SN74CBT3251#order-quality

I looked at the page and it offers:

  1. SSOP (DB)
  2. SSOP (DBQ)
  3. TSSOP (PW)

I have this IC and i have it soldered on a SSOP16 breakout board.

Here is a picture of it.

enter image description here

I don't know which package to choose to buy.

I read the datasheets of the specific packages and they all appear to be the same.

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  • \$\begingroup\$ Get a vernier caliper and measure what you have. Then compare with the datasheet. Body size is right there on the very first page. However, very likely SOIC will be cheapest. \$\endgroup\$ – Indraneel Nov 27 '20 at 0:43
  • \$\begingroup\$ TSSOP is thinner than SSOP, but I'm not sure what the difference between 1 and 2 is. \$\endgroup\$ – Hearth Nov 27 '20 at 0:44
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From the ti.com 74cbt3251 datasheet

There are package drawings at the end of the datasheet. TI has their own set of package codes, but they do also make reference to the JEDEC industry standard package codes as well. The most important parameters from the package drawings are pitch and body width.

Page 20 package drawing for SSOP (ti.com suffix DB, package code DB)
JEDEC MO-150-AC
pitch e=0.65mm, width=5.3mm

Page 22 package drawing for SSOP (ti.com suffix DBQ, package code DBQ0016A)
JEDEC MO-137 AB
pitch e=0.635mm (which is unusual), width=3.85mm

Page 17 package drawing for TSSOP (ti.com suffix PW, package code PW0016A)
JEDEC MO-153-AB
pitch e=0.65mm, width=4.4mm

The sparkfun breakout board in the photo looks like it may be designed to accommodate a range of body widths, but requires the correct pitch. The most common SSOP pitch is 0.65mm, but I have also seen 0.5mm and even in rare cases 0.8mm. A pitch of 0.635mm is probably not what you want, if you're using a standard breakout board.

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  • \$\begingroup\$ Thank you! I said i will buy the 0.65mm parts, and not the 0.635 part as you said. But then i remembered, i had soldered another IC on that adapter. The OPA4353EA. So i went to its TI webpage and the only available part is DBQ, which is the 0.635 mm!(ti.com/store/ti/en/p/product/?p=OPA4353EA/250) So perhaps this is the one i should get. Interestingly enough, i went to see its datasheet, and on the pitch, it says 0.64 mm (digchip.com/datasheets/parts/datasheet/477/OPA4353EA_250.php). So i really don't know which one i should get. Why does this has to be so complicated? \$\endgroup\$ – user1584421 Nov 29 '20 at 0:01

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