Technical Notes

Short circuit resistance

LS circuits don't have output shorting in absolute maximum ratings and have Ios specified (shorting current). Printed TI catalogue. 74VHC161284 datasheet shows that even control lines cannot be shorted down in some implementations.

Speed issues in control lines

ftp://ftp.armory.com:/pub/user/rstevew/LPT/zha96lpt.faq "=> 1 1 -Strobe C0- Set Low pulse >0.5 us to send"

PCB editing details

Precision class

minimum line and space width is 0.3mm. Excerpt from /usr/local/share/pcb/Pcb file (the file is possibly located in different directory):

Pcb.Bloat:                  1378
Pcb.minWid:                 1182 
Pcb.Shrink:                 400 
Pcb.minSlk:                 800

Silkscreen masking out

Solder mask is used to mask out silkscreen by manufacturer for construction class 0.3mm space, 0.3mm trace. At least by that manufacturer by which I had it done.

Packages

I needed to create couple of packages for PCB. They are in the directory packages.

Send feedback to