I am making a circuit with a microcontroller that has a periodic need to save about 500 bytes of information in a non-volatile storage. Running only on a supercap that might be charged up rarely, the microcontroller wakes up periodically,
takes some readings and then writes those items to either an off-chip EEPROM via SPI communication, or to a block of its own flash memory.
I stumbled across this type of chip from Cypress – http://www.cypress.com/products/f-ram-nonvolatile-ferroelectric-ram
The F-Ram chips also use SPI as well, but most of the advantages over EEPROM or Flash writes, like faster write speed, no special voltage or current requirements, 100 trillion cycle endurance, and many others
made me wonder if it was too good to be true. I read the data sheet and it shows that the cells are destroyed by a read but the chip takes care of writing the value back to the cell on reads.
Other than the need for an external chip (vs on-chip Flash in the micro-controller) I could find nearly no drawbacks to using F-ram type devices for what I want to do. Does anyone else know of any disadvantages to using F-ram over EEPROM or Flash?
Best Answer
It's more expensive and not available in really large sizes.
Compare e.g. http://www.digikey.co.uk/product-detail/en/cypress-semiconductor-corp/FM25V10-G/428-3323-ND/3788992 vs http://www.digikey.co.uk/product-detail/en/stmicroelectronics/M95M01-DFDW6TP/497-15781-2-ND/4357400 - the FRAM part is faster but almost 10 times as expensive.
It's found a nice niche as a replacement for battery-backed SRAM and in heavily used dataloggers, but it's not ready to obsolete EEPROM.