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I'm using a M48Z02, a 5 V 16 Kbit ZEROPOWER SRAM.

In absence of power, according to datasheet information, this device can hold data for years:

A [...] package houses the M48Z02 silicon with a long-life lithium button cell to form a highly integrated battery-backed memory solution.

The M48Z02 button cell has sufficient capacity and storage life to maintain data functionality for an accumulated time period of at least 10 years in the absence of power over commercial operating temperature range.

What I'm experiencing is a problematic data loss that make this chip untrustworthy.

I've created a small circuit using a stripboard to only read the M48Z02. I manage the circuit through an ON/OFF switch that connect the power source.

This schematic should explain:

schematic

simulate this circuit – Schematic created using CircuitLab

About 5 hours ago I've programmed my SRAM and than inserted it into the stripboard manager. Now, when I wake it up it shows wrong data in some addresses.

My questions:

  • Is possible that the battery failed and data were corrupted?

  • Is possible that some data were corrupted switching it on and off because of power pins are directly connected with control pins? If yes how avoid that?

NOTE: I presume that this isn't a problem about a buggy chip because 3 M48Z02 of mine have this problem.

EDIT:

a)

What is a stripboard manager?

A "case" for the chip that helps to manage it:

Stripboard manager

b) When I say switch on/off I mean:

  • my power source is OFF and the chip is in his case.
  • I power ON the circuit
  • after reading data I switch OFF the power source
  • the chip is disconnected and (maybe) programmed again

c) About the heat:

I've noticed that when it fail or if I switch on/off power source frequently it becomes hot. Also it becomes very difficult to write new data on the device... but not impossible.

Any help you can provide will be really appreciated.

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Is possible that the battery failed and data were corrupted?

Yes, it is possible. Are you following the procedure in the datasheet to check for low battery voltage? Depending on your source for these ICs (e.g. official or not), the chances of battery problems changes, in my experience.

However, your description may point in a different direction:

About 5 hours ago I've programmed my SRAM and than inserted it into the stripboard manager. Now, when I wake it up it shows wrong data in some addresses.

So you've been powering-on/off the ICs. Notice that on page 12 of the datasheet, they discuss a specific situation which can result in data corruption:


enter image description here


Notice specifically the part which says: "These negative spikes can cause data corruption in the SRAM while in battery backup mode."

Therefore I suggest you follow their recommendation for a Schottky diode and decoupling capacitor as shown in the datasheet, and re-test.

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  • \$\begingroup\$ Thank you for the answer. I can't find anywhere how to check for low battery... \$\endgroup\$ – xdola May 12 '16 at 15:55
  • \$\begingroup\$ @xdola - That procedure to check for a low battery is described in section 2.3 of the datasheet which you linked, with a flowchart of the code you need to implement in Figure 7 on page 11. Hope that helps. \$\endgroup\$ – SamGibson May 12 '16 at 16:09
  • \$\begingroup\$ I will try the protection circuit, but I've a question. What about the temperature? Usually when it fails it also become really hot (50/60 Celsius). Do this mean something? \$\endgroup\$ – xdola May 12 '16 at 18:10
  • \$\begingroup\$ @xdola - "Usually when it fails it also become really hot (50/60 Celsius). Do this mean something?" - This is the first time you have mentioned that behaviour; more details are needed (and those details might then change my hypothesis). I suspect latch-up may be the cause of the heating, triggered by the excessive negative Vcc spikes mentioned earlier. There is also a risk that devices which have heated in that way, have now been damaged (e.g. life-shortened). In other words, adding the protection now might be too late for those ICs you currently have, even if it's the correct solution. \$\endgroup\$ – SamGibson May 12 '16 at 18:51
  • \$\begingroup\$ @xdola - You said: "I've programmed my SRAM and than inserted it into the stripboard manager". (a) What is a "stripboard manager"? I know stripboard, but not "manager" in this context. (b) Is the power switched off to the circuit / "stripboard manager" (whatever it is) when you insert the programmed SRAM into it, or are you plugging the SRAM into a circuit which is already powered? (c) Can you supply the full schematic of the device into which you are plugging the SRAM? Or, if not, then at least some photos and more description of its function and how it is used? \$\endgroup\$ – SamGibson May 12 '16 at 19:12

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