Alternative for a M48Z128Y-120

In a SONY CRT G70 there is a NOVSRAM M48Z128Y-120.
It appears this Dallas chip is no longer available.
In an AVS Forum there is a thread dedicated to replacing the Dallas chip in the G90 (the model after the G70), and there is a side discussion where one user has posted that DALLAS/MAXIM DS1245Y-120+ is a suitable alternative to the M48Z128Y-120. This is what I would like to confirm.

Hello MJH,
Welcome to the DigiKey TechForum.
I was able to find the datasheet for the M48Z128Y-120, linked HERE.
It does appear to confirm that DS1245Y-120±ND would work as a suitable alternative for the obsolete part.

thanks Nick

I have purchased a DALLAS/MAXIM DS1245Y-120+
When I plug this SRAM into to my EPROM Programmer it appears that there is already some information on this SRAM. Some images are attached. Are you able to clarify what is going on? Should it just be a blank chip? Thanks MJH

Yes, I would agree with you that the DS1245Y-120+ as PARALLEL Non-Volatile-SRAM IC with 1Mbit density in 32EDIP from Analog Devices Inc./Maxim Integrated should really just be a blank chip when delivered. I cannot explain the information on this SRAM with your images attached. Did you order just one single part to check this alternative vs the Obsolete STMicroelectronics 128k x 8b organized memory Integrated Circuitry M48Z128Y-120 ?

Hi Rolf, I have been through this ordering process twice now. with DigiKey (with the same issue)
rd 1; I ordered part number S1245Y-120±ND (this is what I want).
It was supplied on invoice number 97823995 (May 2023).
rd 2; this transaction was on invoice number 102099436 (5th January 2024).
Is there something that I am doing wrong in placing the order?
What needs to happen so that I get new ICs? Thanks

Sorry to hear, is your EPROM Programmer capable of doing some kind of blank check in advance of starting the programming process ?
With your attached images I would say that the parts are recognized correctly.


As an authorized distributor for Analog Devices (and the former company Maxim) the DS1245Y-120+ you ordered from us would have come straight from their factory new. They are not used parts.

I have not yet found any hard documentation to back this up, but as an SRAM chip, it seems quite likely that the default state of any memory data bit is indeterminate (metastable) when shipped from the factory and initially powered, since it is volatile memory consisting essentially of flip-flops. The battery back-up does not work until the chip is placed in-circuit and powered up, so it will not retain any initial “factory” value. It will only retain values once it has been powered up in-circuit. It might be possible to design in a feature to automatically clear all bits on initial power up, but I don’t believe this is a universal feature in SRAM chips, and furthermore would be undesirable in an NVSRAM chip anyway.

With a circuit using a “normal” SRAM chip, part of any power-up initialization sequence performed by an in-circuit processor would be to clear all data before doing anything useful. For you, it would make sense to clear it with a programmer, program any initial values you want, and then install in the product.

I did find a thread on the Electronics Stack Exchange which talks about this for standard SRAM. I suspect it is applicable for this part as well.


thanks David,
Whilst it’s plausible that indeterminate bit state is on the chip, the issue I might have is whether the battery has been activated or not.
If it’s not activated, I would expect every time I did a blank check (which is what you see in the attached), that I would retrieve different readings every time.
But since every time I read it in the programmer (note, I have not written anything to it yet), I get the same data shown.
I am surmising that the battery is active, and has been for some time.
Is this truely what is happening?

This is my only concern, that the battery has been activated .
If not, then all is good.
Thanks MJH


According to the datasheet, the chip has a sensing circuit which keeps the battery disconnected until it reads greater than 4.25V on Vcc, at which time it enables the battery back-up system. See page 2 of the datasheet under “Freshness Seal”.

When you connect the chip to a reader/programmer, it would have to apply a valid voltage on Vcc to be able to read/write from/to the chip. Therefore, at that point, the sensing circuit is triggered and the battery is activated and will maintain memory values when power is removed from the chip.

Best regards, David

Hi David, the activation of the battery is a primary consideration, as I will be making a note in my calendar to replace this chip 10 years after that event.
So just to confirm, if I do a blank check only, it activates the battery?
Your guidance is appreciated, regards MJH

From the linked data sheet:

When VCC is first applied at a level greater than 4.25 volts, the lithium energy source
is enabled for battery back-up operation.

So all it takes is applying power to the device.

Since all operations require applying power, all operations activate the back-up battery.

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@PaulHutch is correct. As soon as you blank check the part, the clock is ticking because the battery circuit is activated.

thank you to David and Paul for your guidance.