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Ferroelectric RAM

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Re: Ferroelectric RAM

#11

Post by kirrent »

kragen wrote: post #6
kirrent wrote: post #5

Earlier quoted context omitted.

That's really not a problem just as it's not a problem in normal RAM. With increased speed and endurance it's a doddle to write back a value after reading with your memory controller even if you're not putting in dedicated refresh hardware. It's really all about density and cost.

Unless you lose power in the interim. Flash doesn't have that problem, and normal RAM has it so badly that we rely on Flash to store permanent data and only use DRAM as an ephemeral cache.

The first datasheet I found for a Cypress FRAM chip gives a required power down rate of at most 30us/V which allows it to continue to provide normal operation protecting data. It's a very easy limitation to live with and engineers often deal with far more difficult problems in unexpected power loss than this.

Re: Ferroelectric RAM

#12

Post by jhayward »

baybal2 wrote: post #10
leggomylibro wrote: post #2

It's great stuff, but still low capacity and high cost in commercial chips. If you want to play with it, check out TI's MSP430FRxxxx microcontrollers. They have FRAM instead of Flash. Also, there are 8-pin FRAM chips with the same pinouts as generic QSPI Flash/RAM/etc chips which you can buy today. Again, it's still low-density and expensive, but that seems to be improving and it's fun to make applications which can…

And destructive reads with limited life cycles, assures a steady recurring revenue for TI...

Trillions of cycles isn't that "limited", compared to e.g. Flash.

Re: Ferroelectric RAM

#13

Post by baybal2 »

jhayward wrote: post #12
baybal2 wrote: post #10

Earlier quoted context omitted.

And destructive reads with limited life cycles, assures a steady recurring revenue for TI...

Trillions of cycles isn't that "limited", compared to e.g. Flash.

FRAM is far from trillions of cycles, more close to billions, which still kills it after ~5-7 years of intense use.

Re: Ferroelectric RAM

#14

Post by jpmattia »

evancox100 wrote: post #7

One of the benefits of FRAM is that you can put it through extreme radiation and still have it work afterwards. So you can put it in a medical instrument that undergoes gamma ray sterilization, and it will still not only work but also retain the data.

> One of the benefits of FRAM is that you can put it through extreme radiation and still have it work afterwards.

There are no oxides in the supporting circuitry? [Do you have a link to rad-hard results?]

Re: Ferroelectric RAM

#15

Post by naikrovek »

baybal2 wrote: post #13
jhayward wrote: post #12

Earlier quoted context omitted.

Trillions of cycles isn't that "limited", compared to e.g. Flash.

FRAM is far from trillions of cycles, more close to billions, which still kills it after ~5-7 years of intense use.

That's more than flash. That's more that an SSD, even, probably.

If you're writing to flash or FeRAM that much it seems to me that You're Doing It Wrong.

Re: Ferroelectric RAM

#16

Post by castratikron »

baybal2 wrote: post #13
jhayward wrote: post #12

Earlier quoted context omitted.

Trillions of cycles isn't that "limited", compared to e.g. Flash.

FRAM is far from trillions of cycles, more close to billions, which still kills it after ~5-7 years of intense use.

No, FRAM really is in the trillions of RW cycles.

https://www.cypress.com/file/209146/download

Re: Ferroelectric RAM

#17

Post by deelowe »

kragen wrote: post #6
kirrent wrote: post #5

Earlier quoted context omitted.

That's really not a problem just as it's not a problem in normal RAM. With increased speed and endurance it's a doddle to write back a value after reading with your memory controller even if you're not putting in dedicated refresh hardware. It's really all about density and cost.

Unless you lose power in the interim. Flash doesn't have that problem, and normal RAM has it so badly that we rely on Flash to store permanent data and only use DRAM as an ephemeral cache.

Because dram loses its memory when powered off not because there's some issue with how refresh works. Needing to refresh memory after a read is hardly any engineering challenge. We've been dealing with it since memory's inception.

Re: Ferroelectric RAM

#18

Post by evancox100 »

jpmattia wrote: post #14
evancox100 wrote: post #7

One of the benefits of FRAM is that you can put it through extreme radiation and still have it work afterwards. So you can put it in a medical instrument that undergoes gamma ray sterilization, and it will still not only work but also retain the data.

> One of the benefits of FRAM is that you can put it through extreme radiation and still have it work afterwards. There are no oxides in the supporting circuitry? [Do you have a link to rad-hard results?]

I only have access to the same public info you would. Here's a technical paper from TI:

http://www.ti.com/lit/wp/sboa154/sboa154.pdf

BTW according to TI's support forum, the MSP430F chips with FRAM are not rated to withstand the high levels of gamma radiation used in medical sterilization.

However, Maxim does have many parts rated for that type of application, with "non-floating gate" NV memories. (Draw your own conclusions about what they are referring to.) https://www.maximintegrated.com/en/app-notes/index.mvp/id/60...

Edit: And of course there are oxides, but you can margin around the assymetric Vt-shift that occurs in the transistors.

Edit 2: At least one part explicitly states in the data sheet that it uses FRAM. https://datasheets.maximintegrated.com/en/ds/DS28E84.pdf

Re: Ferroelectric RAM

#19

Post by zaarn »

baybal2 wrote: post #13
jhayward wrote: post #12

Earlier quoted context omitted.

Trillions of cycles isn't that "limited", compared to e.g. Flash.

FRAM is far from trillions of cycles, more close to billions, which still kills it after ~5-7 years of intense use.

What microcontroller will see continued and "Intense" use of it's internal flash?

The worst I do to mine is to log sensor data in absence of wifi, that's in the order of bits/minute.

Re: Ferroelectric RAM

#20

Post by LocalH »

Fun fact: Sonic 3 for Sega Megadrive/Genesis used FeRAM as save RAM. Generally, a Ramtron FM1208S-200CC. I think a few other carts of theirs used it, I've seen 32X Virtua Racing carts with Ramtron FeRAM parts.
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