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

Ullrich Peter Peter.Ullrich at kapsch.net
Sun Apr 25 21:53:08 CEST 2021


The good old but useful MAX691 are also still in production.

https://www.maximintegrated.com/en/products/power/supervisors-voltage-monitors-sequencers/MAX691.html
MAX691 Microprocessor Supervisory Circuits - Maxim Integrated<https://www.maximintegrated.com/en/products/power/supervisors-voltage-monitors-sequencers/MAX691.html>
The MAX690 family of supervisory circuits reduces the complexity and number of components required for power supply monitoring and battery control functions in microprocessor systems. These include µP reset and backup-battery switchover, watchdog time
www.maximintegrated.com


https://datasheets.maximintegrated.com/en/ds/MAX690-MAX695.pdf
MAX690MAX695 Microprocessor Spervisory Circits<https://datasheets.maximintegrated.com/en/ds/MAX690-MAX695.pdf>
VCC = full operating range, VBATT = 2.8V, TA = +25°C, unless otherwise noted.) Note 1: The input voltage limits on PFI and WDI may be exceeded provided the input current is limited to less than 10mA. Note 2: WDI is guaranteed to be in the mid-level (inactive) state if WDI is floating and VCC is in the operating voltage range. WDI is internally biased to 38% of VCC with an impedance of ...
datasheets.maximintegrated.com

Ciao
Peter


________________________________
Von: Synth-diy <synth-diy-bounces at synth-diy.org> im Auftrag von Jean-Pierre Desrochers <jpdesroc at oricom.ca>
Gesendet: Sonntag, 25. April 2021 17:59
An: Synth-diy at synth-diy.org <Synth-diy at synth-diy.org>
Betreff: *EXT* [sdiy] Substituing M48Z18-100 (equ of DS1225AB-100) with 28 pins DIP small pcb .. found something..


I think I’ve found 2 IC’s that could do the job (I think..)



SRAM non-volatile controller in 8SOIC package:

BQ2201SN-N

https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=&ved=2ahUKEwiasOzR35nwAhVqGFkFHTluCykQFjAAegQIAxAD&url=https%3A%2F%2Fwww.ti.com%2Flit%2Fgpn%2Fbq2201&usg=AOvVaw06LYSkBSK_1TQIIAxQiouX<https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.google.com%2Furl%3Fsa%3Dt%26rct%3Dj%26q%3D%26esrc%3Ds%26source%3Dweb%26cd%3D%26ved%3D2ahUKEwiasOzR35nwAhVqGFkFHTluCykQFjAAegQIAxAD%26url%3Dhttps%253A%252F%252Fwww.ti.com%252Flit%252Fgpn%252Fbq2201%26usg%3DAOvVaw06LYSkBSK_1TQIIAxQiouX&data=04%7C01%7CPeter.Ullrich%40kapsch.net%7C15e3d4bf1cab402ba06908d90805501a%7C5f9ce5277e3e4e83a8a4b6c848f85ab5%7C1%7C1%7C637549641189051369%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000&sdata=0EkUrZ5CIXKbNMB5%2FIVrMpneydyFm9%2BV1hBzE%2Bp3zbw%3D&reserved=0>



SRAM 8K x 8 ( Data retention voltage :1.5V min) in 28SOP package:

AS6C6264-55SCN

https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=&ved=2ahUKEwidspDy35nwAhUNGVkFHbHkDlUQFjADegQIAhAD&url=https%3A%2F%2Fwww.alliancememory.com%2Fwp-content%2Fuploads%2Fpdf%2FAlliance%2520Memory_64K_AS6C6264v2.0July2017.pdf&usg=AOvVaw1OWQu_vBHdlEtp0o5PSFeO<https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.google.com%2Furl%3Fsa%3Dt%26rct%3Dj%26q%3D%26esrc%3Ds%26source%3Dweb%26cd%3D%26ved%3D2ahUKEwidspDy35nwAhUNGVkFHbHkDlUQFjADegQIAhAD%26url%3Dhttps%253A%252F%252Fwww.alliancememory.com%252Fwp-content%252Fuploads%252Fpdf%252FAlliance%252520Memory_64K_AS6C6264v2.0July2017.pdf%26usg%3DAOvVaw1OWQu_vBHdlEtp0o5PSFeO&data=04%7C01%7CPeter.Ullrich%40kapsch.net%7C15e3d4bf1cab402ba06908d90805501a%7C5f9ce5277e3e4e83a8a4b6c848f85ab5%7C1%7C1%7C637549641189061364%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000&sdata=XOsKdB4JsJxucvhMLtiIBh5ofPljhMPbGrES4fBwkCw%3D&reserved=0>

Both IC’s cost not exceeding $15.00CAD !

The connections between both IC’S is simple:

[cid:image001.png at 01D739CA.258B4460]

But I will use only one battery connected at BC1, (BC2 tied to VSS).



Should I use any supply 0.1uf + 10uf caps on the final small pcb. ?











*************************************************************************



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.

[cid:image003.png at 01D739C1.784777E0]



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&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<https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.google.com%2Furl%3Fsa%3Dt%26rct%3Dj%26q%3D%26esrc%3Ds%26source%3Dweb%26cd%3D%26ved%3D2ahUKEwiDl_DKzZnwAhVdElkFHZaBCTsQFjABegQIAhAD%26url%3Dhttp%253A%252F%252Fworldphaco.com%252Fuploads%252FTEKTRONIX_2465b_OSCILLOSCOPE_CALIBRATION___REPOWERING_THE_DS1225.pdf%26usg%3DAOvVaw1WP8nMcsFuEALX2uMw2rP1&data=04%7C01%7CPeter.Ullrich%40kapsch.net%7C15e3d4bf1cab402ba06908d90805501a%7C5f9ce5277e3e4e83a8a4b6c848f85ab5%7C1%7C1%7C637549641189061364%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000&sdata=mZuDKIUN3kP2I7ymDv6c8FJV6%2FTAvS%2BtK%2FL86cgvcdo%3D&reserved=0>

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:

[cid:image002.jpg at 01D739C1.B7188DB0]

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://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.tindie.com%2Fproducts%2Fglitchwrks%2Fglitch-works-gw-1225-1-dallas-ds1225-replacement%2F&data=04%7C01%7CPeter.Ullrich%40kapsch.net%7C15e3d4bf1cab402ba06908d90805501a%7C5f9ce5277e3e4e83a8a4b6c848f85ab5%7C1%7C1%7C637549641189071353%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000&sdata=3q0xzHQwYk6EOFE20JG08yTc6H5Z8pDfKSMFMqbHDLI%3D&reserved=0>

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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