what is a SOIC 300 mil and a SSOP 208 mil pakage ?

[Thunderchild]

these are referenced to pics 18F88

 

[Oznog]

Um, they're packages??
The pkg dimensions are probably listed in the back of the spec sheet. Otherwise those are std pkgs you can look them up anywhere.

 

[dknguyen]

Chip

It is telling you what the chip looks like on the outside.

 

[philba]

both are surface mount IC packages.

note that there are several SOIC footprints, wide and narrow(normal? I dunno). It's easy to get them mixed up when you layout a board. Not fun to get your board and discover you used the wrong footprint.

 

[Thunderchild]

so are they practical ? is ask because the only way to get the 16F88 (at least as a free sample) with 20 pins rather than 18 is in the second shape. fankly my only mthod at the moment is wires so I think I can only use the DIP type pakage. by the way any precautions i should observe wiring a pic I know the frequenzy is not that high so I pressume not eh ?

 

[dknguyen]

PICs are pretty simple to wire up. SOIC is about as practical as they get for surface mount packages...

YOu say your only mounting option is wires? What are you doing? Breadboarding? Wire-wrap? I think you can get sockets...but they cost more than if you just buy the DIP version of the IC.

 

[Nigel Goodwin]

so are they practical ? is ask because the only way to get the 16F88 (at least as a free sample) with 20 pins rather than 18 is in the second shape. fankly my only mthod at the moment is wires so I think I can only use the DIP type pakage. by the way any precautions i should observe wiring a pic I know the frequenzy is not that high so I pressume not eh ?

Why would you want a 20 pin package?, the 16F88 is an 18 pin device, the 20 pin surface mount version has two unused pins to make the 20.

I suggest you use the conventional 18 pin DIP package!, personally I don't like using breadboards, but it should be fine for reasonable frequencies - even 20MHz may be OK?, but it's pretty high for a bread board.

 

[dknguyen]

Unfortunately, the only thing that differs when a device is using a different package is the package. The same silicon die is used inside so all the pins are exactly the same, just in different places, and unused pins becomes just that.

 

[philba]

The SOIC F88 is 18 pin. the SSOP is 20 pin though not with NCs but rather the 2 extra pins are used for analog Vss and Vdd. It may allow somewhat better noise rejection since you could connect them to the digital side through ferrite beads.

I kind of wish they'd broken out the PGC and PGD pins but I guess it would be a different die then. I know they do it on other chips, though.

by the way, I use solderless breadboards (SBB) for 20 mhz PICs all the time. It works just fine. the one area you have to be aware of is the analog inputs which can be noisy because the SBB rails capacitively couple to adjacent rails. I usually ground all the unused rails. helps a little. I typically see 1-2 LSBs improvement from SBB to PCB.