Hi all,
For a few days now I've been researching and developing a board for making a functional replacement for the DS1486 and DS1250.
I've had the ebay woes like many of us here and just can't seem to find a source for any NOS 2008 or 2009 date coded modules (which is when they stopped production?), and the nearly $100 cost for a genuine new DS1250 is just ridiculous.
First, about the DS1486:
I tore apart one of my DS1486s that is genuine, and as many of you guessed it is simply a low power SRAM chip with a DS1384FP acting as the controller, a 32khz crystal, and two tabbed BR1632 lithium cells sitting on top of the two chips. The DS1384FP (44pin 10x10mm QFP) is unobtainium as well, but I was curious about a number of sellers selling something labeled DS1384G which is a 48pin 7x7mm QFP. I was sort of expecting this to be a sanded and relabeled DS1558 or something else entirely, but after looking at several pictures of the DS1386P and DS1486P Powercap modules you can actually see a 48pin QFP on them labeled DS1384G. I'm inclined to think this may have been an internal production part that Dallas made to get the smaller, thinner footprint of the 7x7 QFP, which also seems about a millimeter shorter in height. I'm consulting Maxim right now to see if I can get a pinout of this chip but so far they don't even seem to know what I'm talking about
Nevertheless, by tracing back pins on those powercap modules and with some help and educated guesswork from the DS1558 datasheet which shares the 48 pin QFP footprint, I think I've figured out the pinout of the DS1384G.
I've made a layout on KiCad that I currently have in production at OshPark and I plan to use the Batten Allen leadframes to create a DIP package out of this and test it out.
I would love to get some feedback on board layout, since this is actually my first ever layout of this type of circuitry (usually doing audio). The layout was pretty difficult with such little board space and so many traces to run.
Also if anyone else has any thoughts on the DS1384G chip and my conclusions, perhaps I can gain some more insight.
About the DS1250:
Once again, this is fairly straightforward in using a run of the mill low power SRAM chip with a DS1312 controller. Actually, the part is labeled DS13C12, which once again, I cannot find any information about so I'm once again guessing it was an internal Dallas production part made for some specific reason. However, the ordinary DS1312 should be a perfectly suitable replacement. I'm using the 8 pin SOIC DS1312-2+. The DS1312 only has inputs for 1 battery which also matches up with the DS1250 only having 1 battery.
I would love to be able to make DS1650 exact replacements too using the (speculated) DS1610 controller, but I've not found any source for that part, and coupled with the fact that Tek scopes don't use the extra functionality it's not really necessary anyway.