[sdiy] Substituing M48Z18-100 (equ of DS1225AB-100) with 28 pins DIP small pcb

Jean-Pierre Desrochers jpdesroc at oricom.ca
Sun Apr 25 22:23:06 CEST 2021


I think I’ll go for the FM16W08-SG as suggested by Jason..
No battery worrying and it seems to fit my needs..
28SOIC package mounted on a SOIC to DIP carrier like this one:



Thanks !

 

 

De : Jason Tribbeck [mailto:jason at tribbeck.com] 
Envoyé : 25 avril 2021 13:00
À : Jean-Pierre Desrochers
Cc : synth-diy mailing list
Objet : Re: [sdiy] Substituing M48Z18-100 (equ of DS1225AB-100) with 28 pins DIP small pcb

 

DS1225 does seem to still be available from Farnell: https://uk.farnell.com/maxim-integrated-products/ds1225ab-70ind/nv-sram-parallel-64kbit-edip-28/dp/2798716

 

Or you could look at FRAM, for example Cypress FM16W08-SG : https://uk.farnell.com/cypress-semiconductor/fm16w08-sg/f-ram-non-vol-64kbit-soic-28/dp/2772905

 

I'm pretty sure FRAM can be used in the same way as SRAM.

 

On Sun, 25 Apr 2021 at 16:02, Jean-Pierre Desrochers <jpdesroc at oricom.ca> wrote:

Hi list,

I need to replace a M48Z18-100PCI (8K x 8 battery backed SRAM) in one of my old
test equipment. It's dated 1996 so It's inner battery life is ending.

Yeah even after 25 years it still keeps its data.. (!!!)

It's a 28 pins 600mil DIP package.



 

The specs say it is full Dallas DS1225 compatible.

There are many sites who show how to hack a DS1225 package
to disconnect the inner battery tabs and connect small leads
to an external battery keeping the still working SRAM.

This for example:

https://www.google.com/url?sa=t <https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=&ved=2ahUKEwiDl_DKzZnwAhVdElkFHZaBCTsQFjABegQIAhAD&url=http%3A%2F%2Fworldphaco.com%2Fuploads%2FTEKTRONIX_2465b_OSCILLOSCOPE_CALIBRATION___REPOWERING_THE_DS1225.pdf&usg=AOvVaw1WP8nMcsFuEALX2uMw2rP1> &rct=j&q=&esrc=s&source=web&cd=&ved=2ahUKEwiDl_DKzZnwAhVdElkFHZaBCTsQFjABegQIAhAD&url=http%3A%2F%2Fworldphaco.com%2Fuploads%2FTEKTRONIX_2465b_OSCILLOSCOPE_CALIBRATION___REPOWERING_THE_DS1225.pdf&usg=AOvVaw1WP8nMcsFuEALX2uMw2rP1


Since my chip is a M48Z18-100PCI it does not have the same 
potted packing of a genuine DS1225 (should it ??) so dremeling it
to reach the battery tabs would be quite hazardous..

 

So here is my question:

I'd like to build a small 28 pins 600mils DIP pcb
who would contain a 8Kx8 SRAM with battery controller IC
the same way the inside DS1225 does it:



DS1218 and DS2064 are now obsolete ICs so this would not be a good choice..

 

A company called Glitch Works has this type of new substitute IC available:

 <https://www.tindie.com/products/glitchwrks/glitch-works-gw-1225-1-dallas-ds1225-replacement/> https://www.tindie.com/products/glitchwrks/glitch-works-gw-1225-1-dallas-ds1225-replacement/

But for me $51.00US including shipping to Canada is too expensive..

But the idea of a small 28 pins DIP pcb module is a good one..
Building it would be fun too !

I’m not an engineer and cannot figure out the DS1225 read/write needs to be taken care of
choosing the right components. Any 8Kx8 SRAM with a 100ns acquisition should do
but the choice of a good battery controller IC and the adequate connections between both IC’s
and the 28 DIP pins to behave exactly like a M48Z18 or DS1225 exceeds my knowledge..

Can you help with some possible IC’s and some easy wirings linking them ?

Many thanks !

 

 

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