why Xmega does not exist in small package (tqfp32)

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Hi all,
Does anyone knows why Xmegas does *not* exist in small packages ?

A tqfp32 XMega for instance would be nice.
A great choice to handle many IO automagically with accurate timings...

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Xmega A4 in TQFP: 10mm x 10mm; 34 I/O

Mega88 in TQFP: 9mm x 9mm; 23 I/O (20 for mere mortals)

You can put lipstick on a pig, but it is still a pig.

I've never met a pig I didn't like, as long as you have some salt and pepper.

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Thanks theusch,
I did not realize that there was so little difference between packaging size.

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There is also the number of pins.
A Xmega A4 may be much more difficult to solder by hand than Mega88, given the ratio number of pins per millimeter.

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Quote:

A Xmega A4 may be much more difficult to solder by hand than Mega88, given the ratio number of pins per millimeter.


1) What does that have to do with your original question?
2) If you are looking for small packages, wouldn't the pitch be less the smaller the package? So you are decrying the lack of small packages, and then saying the small packages are too small?
3) The pitch is the same between the Mega88 TQFP32 and Xmega A4 TQFP44. So what are you questioning?

You can put lipstick on a pig, but it is still a pig.

I've never met a pig I didn't like, as long as you have some salt and pepper.

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Hi theusch,
Again, thanks for taking time to answer.

theusch wrote:
Quote:

A Xmega A4 may be much more difficult to solder by hand than Mega88, given the ratio number of pins per millimeter.


1) What does that have to do with your original question?
2) If you are looking for small packages, wouldn't the pitch be less the smaller the package? So you are decrying the lack of small packages, and then saying the small packages are too small?
3) The pitch is the same between the Mega88 TQFP32 and Xmega A4 TQFP44. So what are you questioning?

tqpf32 = 8 pins per side = 8 pins on 9mm = 0.88 pin/mm
tqfp44 = 11 pins per side = 11 pins on 10mm = 1,1 pin/mm

So ratio pin/mm: tqfp44 > tqfp32

In my view, an Xmega with 32 pins would be "easier" to use for hand made small circuit, and may be cheaper also. Xmega are very nice processor, and I would like to use them everywhere :)

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Quote:

tqpf32 = 8 pins per side = 8 pins on 9mm = 0.88 pin/mm
tqfp44 = 11 pins per side = 11 pins on 10mm = 1,1 pin/mm

So ratio pin/mm: tqfp44 > tqfp32


Why are you "guessing" about these things?

Go to the datasheets. Look at the Packaging Information.

For the two models that I referred to, "e" is the distance between the centers of two adjacent TQFP pins. It is 0.8mm in both cases.

Dividing "E" by the number of pins doesn't tell you much, unless you know "E1" and the not-given dimension between the edge of the package and the first pin.

(While 0.5mm may not be a lot of fun our bench people proficient at 0.8mm can do 0.5mm without undue problems, using the same techniques.)

You can put lipstick on a pig, but it is still a pig.

I've never met a pig I didn't like, as long as you have some salt and pepper.

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Quote:

tqpf32 = 8 pins per side = 8 pins on 9mm = 0.88 pin/mm
tqfp44 = 11 pins per side = 11 pins on 10mm = 1,1 pin/mm

So ratio pin/mm: tqfp44 > tqfp32

Rubbish.

The data sheets are clear. The pin-to-pin distance, pitch, or whatever you like to call it, is:

ATmega88A, TQFP32: 0.80 mm (typical)
ATxmega16A4, TQFP44: 0.80 mm (typical)

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In other words,
on a PCB the tqfp44 requires more space for pins and routing, than the tqfp 32. Of course !
But when those suplementary pins are not used, it will waste some space on the pcb layout.

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I have clues that you did not actually go to the datasheets involved. As I was getting the numbers for the latest go-round I noticed that I used the E1 instead of the E for TQFP44. The total size comparison is actually E of 9mm for TQFP32 and 12mm for TQFP44. So your original question/premise is indeed true--the smallest Xmega A4 in TQFP is ~75% larger than TQFP32. So, true enough if those 63 mm2 are vitally important.

You can put lipstick on a pig, but it is still a pig.

I've never met a pig I didn't like, as long as you have some salt and pepper.

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Well,
I did look at xmega datasheet, but did not checked again atmega88. Yes the difference is in fact 3mm per side.

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Quote:

I did look at xmega datasheet,

Then why were you attempting to calculate pin pitch versus using the diagram/table?

Anyway, I don't know if the Xmega will ever be targeted to the 8, 20, or even 32 pin arena. (Many of us would be happy if they just provided a stable product line with few/no major errata.) And for an "advanced" AVR design I probably don't have any problems with TQFP44 size. I'd think that true tiny-sized designs nowadays would then use the MLF.

You can put lipstick on a pig, but it is still a pig.

I've never met a pig I didn't like, as long as you have some salt and pepper.