Need a small IC or circuit for SPI level translation (5V master to 3.3V devices)

[Papabravo]

?? I screwed you !!??
That's a little bit severe
Why is the US8 package a problem?

 

[kchriste]

Papabravo, j/k means Just Kidding.

 

[futz]

?? I screwed you !!??
That's a little bit severe
Why is the US8 package a problem?

Note the "j/k" at the end, meaning "just kidding".

 

[Papabravo]

Well I took pity and went to the TI website to find the LVC3G34 and the LVC3G17 in what I think are likely to be SOIC-8 packages. the package code is DCT.

https://www.electro-tech-online.com/custompdfs/2008/02/sn74lvc3g34.pdf
https://www.electro-tech-online.com/custompdfs/2008/02/sn74lvc3g17.pdf


j/k is a kind of a flip-flop. Not all of us speak shorthand text. You would be well advised to avoid things which can be misunderstood.

Maybe it would be easier if I just came to work for you -- eh?

 

[iso9001]

I learned j/k is a flip flop and you learned it means joking

I sent you a PM if you are interested in work.

Yea, I saw those "DCT" packages but I didn't think they were SOIC-8, I think unless it goes by another name there seem to be large and small US8 packages.

The distance between pins on the SOIC should be 1.27mm (0.050"), the larger 'dct' package has that dim speced at half that or 0.65mm (0.025"). The smaller DCU is .5mm spacing.

The picture at the top makes the package look like an SOIC8 then a US8, then then whatever that small package is. According to the spec though its large US8, small US8, and then the other.

To answer your question about why us8 is a problem, the prototype pcbs are being made and the pad was drawn to soic8. Its not a huge problem because its an optional part of the board. There are bypass resistors I can use. I probably should have done a more expensive BOM before, but I ran out of time,


What I find very odd is that there seem to be no SOIC-8 no inverting triple buffer packages. Strange.

There are some pin compatible 5V tolerant schmitt trigger buffers in SOIC8, I'll have to see if those will work for SPI (I think it will as long as the propagation and hysteresis match up)

Edit: Nope, apparently now I can't find any SOIC8 schmitts now either.... also, LOL @ my reputation for inappropriate comment

 

[Papabravo]

'saright -- my skin is actually pretty thick. I was certainly taken in by the pictures and did not look closely at the mechanical drawings. If there is not a market for it then I guess they won't make it. Still I'm a bit surprised.

 

[iso9001]

I'm more then surprised - shocked really.

Its ok, I've decided that to fix problems like this in the future I'll just switch to 3V or 1.8V chips. Should help with power management anyhow,

I left my options on this board open, so I'll try a couple zeners, 5V chips, and maybe some other tricks.... for a larger run I'll just have to use a US8