8TSSOP size standard in chaos now?

The SOT505-2 seems to be a Philips creation.

Cheers

Digikey's package descriptions are chaotic.

Sure, but if the two major players NXP and TI have a very different definition of what TSSOP means thing get scary. That greatly increases the chance for a layout that results in useless boards.

I have known for some time that chip packages vary between companies. There is a standard, then there are the parts you buy. I've never used this particular package which seems to have rather extreme variations, but I have seen smaller variations before. That is why I always verify every part footprint I use. "Standard" package libraries are a joke and not just because they can have errors.

"TSSOP" is more a category than a specific package.

I'll just design it per datasheet and call one package 8TSSOP-NXP and the other 8TSSOP-TI. What a sad state of affairs. In the old days 16-DIP meant 16-DIP and it was always the same. Now it's chaos.

Another way would be to make a smaller package with really long pads but then assembly houses might complain.

The fact that NXP has two more packages in the datasheet that are very different and calls both of them XSON8 does not increase my confidence level.

My current product uses a switch device in a TSSOP package. The only difference with a SSOP package is the width so I made the pads cover the area of both packages to allow a Maxim part to be used if needed. At least it gives a second source and the Maxim part goes high impedance when powered down which the customer may need some day. The board house has never complained. That doesn't say they won't complain if I try to use the SSOP package. In general they are very accommodating and I don't expect any trouble.

We have a different footprint file for every part in the library (with probably a generic one for each resistor/capacitor manufacturer but I don't know that detail). The norm is to use the manufacturer's recommended footprint so if there are two manufacturers for a part they will have different footprints.

Really, for anything not SOIC, I pull the datasheet and find the package drawing dimensions and check it carefully. There are all sorts of variations in package and lead shapes.

I use Digi-Key as a great source of datasheets. They have a full datasheet on almost every item they sell. Many others have extremely cursory data sheets or nothing at all.

Jon

Sometimes the manufacturer aggregate all the boring mechanical drawings and footprint stuff into one document. Sometimes they make minor-ish changes to the packaging. Someone should keep on top of that stuff. If you're qualifying two suppliers and the packages are slightly different but close enough that one footprint can realistically do, split the difference or something.

For semis, I always follow the exact part number to the exact drawing (and consider the recommended footprint, if provided) for that particular manufacturer.

Ideally, you should change the footprint slightly even if a substitute passive like a capacitor is a bit taller or shorter than the original, but usually it doesn't make that much difference to the yield AFAICT.

--sp

It gets sold as either TSSOP or XSON. I guess after the order it'll be like what Forrest Gump used to say, "life's like a box of chocolates, you never gonna know what you gonna get".

I'll have to do that as well. What a mess. In the old days one you simply pick a footprint from a library and marry it to the device. No more :-(

It is also a major cost factor if qualifying a 2nd source requires a whole new board spin.

By "old days" you mean devices that were measured in inches and not mm? Yeah, I also remember the $0.25 Coke, but you don't see that anymore either.

Sure but we don't do second sources. If we need another source, a board spin is *way* down on the list of worries.

I mean things like DIP packages. They are always the same no matter which brand. Same with tube sockets.

That can become a problem. There are designs of mine where 2nd source was mandatory, for good reasons.

Not in a high volume business when suddenly component XYZ became unobtanium. Like it happened yesterday but 15 minutes later that client had the info what alternate part to buy where a million is in stock. I barely had to tap the brakes on another project to do that.

Does you mountain bike have the fat tires they used back in the days of DIPs and tubes?