I'm hoping someone may be able to explain to me why are there extra pads on the bottom of APXW003 DC/DC SMPS PCB mount module from ProLynx series from GE Industrial. I am doing a design and it turns out cheaper for me to use these modules than to make a SMPS from discrete parts.
The datasheet, which can be found here:
http://apps.geindustrial.com/publibrary/checkout/APXW003A0X?TNR=Data%20Sheets|APXW003A0X|generic
makes no mention of the circular pads which can be seen in the land pattern presented on page 19 of the document. I have ordered a few of these modules and checked for continuity of these pads, and found it to be as in the picture attached (two of them connect to GND, one of them connects to VIN). I have read the datasheet twice carefully and was not able to find any mention of these except on page 19 where they are just labelled "keepout".
Could someone explain to me the function of these pads? Should I connect them to GND and VIN on the PCB as I have found (with a multimeter) they are internally connected to those pads? They strike me as very strange as solder can easily bridge a pad and those circular "keepout" marks – especially the one between "VS+" and "VOUT". What is their function?
Thank you!
-Igor
Best Answer
My guess is they are pogo-pin-test-bench test points.
I'd be amazed if one of the "GND" ones isn't in some way Vout or related to it.
They use those to test the module in an automated jig to see if it works as intended, BUT...
You cannot use them reliably, because you have no knowledge of what they are connected to exactly. One may be connected to GND directly, or it may have a buffer component like a 1Ohm resistor for some unknowable reason.
I think it's a bit sloppy to put them so close to actual pads and not even mention a DNC notice on a few more pages, but, companies these days get to be a little sloppy some times.