STR912

ma99lo · ‎2008-03-24

Posted on March 24, 2008 at 12:37

STR912

ma99lo · ‎2011-05-17

Posted on May 17, 2011 at 09:41

HI all, we are designing a board using the STR912FW44. now we have a serious problem with the PCB footprint package. on the data sheet we see: e (pin to pin step) = 16 mils. pin width= 7 mils (typ). if we do 16 pin X 31 (steps 16) and measure the centre pin1 to pin 32, we have 496 !!! more than one pin more than 488, as it should be !!! which are the correct measures? have you the footprint already done for Layout?? at the moment we are stopped the development of the application because we cannot solve it ! thanks a lot !! :( :(

roger_lynx · ‎2011-05-17

Posted on May 17, 2011 at 09:41

if we do 16 pin X 31 (steps 16) and measure the centre pin1 to pin 32, we have 496 !!! more than one pin more than 488, as it should be !!! which are the correct measures?

No need to panic, if you work with metric dimensions, the table is correct (page 70, Rev 3);

namely 0.4 mm x 31 = 12.40 mm = D3 = E3.

The problem is rounding error in conversion from metric to inch, since 0.4 mm = 15.746 mil and not 16 mils as shown.

So take 15.746 mils x 31 = 488.189 mils, the table shows 0.488''. Close enough, oui?

If you adjust your grid to mm for the footprint, you'll be okay.

mohamed23 · ‎2011-05-17

Posted on May 17, 2011 at 09:41

Dear all,

I have desinged my PCB design but using the metric table and it is correct. So I confirm that is a rounding error from mm to inch , this should be escalated to ST ;)

Thanks for the clarification :-]

Rave

ma99lo · ‎2011-05-17

Posted on May 17, 2011 at 09:41

WOW, good !!

thanks a lot for all.!! :) :)

gennadiy_grinberg · ‎2011-05-17

Posted on May 17, 2011 at 09:41

Somebody has STR912FAW42X6 footprint for Orcad?

I thank you in advance.

Best regards