This PCB will let you convert a Dallas DS1220 non-volatile SRAM chip to an FRAM chip that does not require backup batteries.

NOTE: You will not be able to program this chip in many chip programmers due to the resulting size/part number mismatch, as the FRAM is twice the capacity of the DS1220 (But is limited to the size of the DS1220 by the PCB design).

To get around this, program the FRAM chip before soldering (this worked for me), or use the instrument/equipment it is being installed into to program it. (I have not tested this).

For use in my 3458A multimeter I programmed the chip before soldering, and once installed into my 3458A it works perfectly.

Just solder the FRAM quickly to prevent it heating up too much. Letting it sit at an elevated temperature (such as reflowing on a hot plate etc) for too long can erase the contents of the memory and require reprogramming. Hand soldering is best for retaining memory contents.

You can use any FM16W08 SMD variant, and be sure to use thin circular pin type header pins such as the examples below:

https://www.ebay.com/sch/i.html?_nkw=2.54+header+round+pin+single+-socket+-female

https://www.digikey.com/en/products/detail/schmartboard-inc/920-0172-01/9559434

The capacitor is not critical, any 0805 ceramic cap will work, Try to use 50V rated part or higher for best performance.

I just specified the cheapest and most available part from Digikey.

Don't use standard square pin header pins as they won't fit! (And will damage sockets you plug them into).

This has been verified as working in a HP/Agilent 3458A Multimeter.