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Serial EERAM: SRAM that Doesn’t Lose Data on Power Down

EERAM is a serial SRAM product that has hidden nonvolatile bits. On any power disruption, the active SRAM array content is moved to the nonvolatile bits.  When power is restored, the nonvolatile content is restored to the SRAM array and SRAM operation continues.

Nonvolatility at the Speed of SRAM

  • Unlimited Reads/Unlimited Writes: Standard SRAM cells and protocol with symmetrical read and write timing
  • Industry-Standard Bus Types: I2C
  • Invisible-to-User Data Transfers on Power Loss: Hidden nonvolatile cells capture SRAM content; power loss is detected automatically by the EERAM device
  • 100,000 Backups: Data can be moved from SRAM to nonvolatile cells > 100,000 times
  • 100-Year Data Retention: With power removed, data is kept safe for up to 100 years; when power is restored, data is moved back to SRAM for continuing operation
  • Quality: EERAM is based on high-volume, standard CMOS processes to create a very low-cost nonvolatile SRAM solution and the highest quality levels

I2C Serial EERAM Products by Density

What is Serial EERAM?

Serial EERAM is a standalone serial SRAM memory that includes shadow nonvolatile backup. EERAM uses a small external capacitor to provide the energy needed to move the contents of the SRAM to the nonvolatile cells when system power is lost. Unlike NVSRAM, no external battery is needed. EERAM offers unlimited SRAM read and write cycles and > 100,000 backups to the nonvolatile cells. The Vcc is monitored inside the IC and can automatically handle the data movement between the SRAM and the nonvolatile memory on any power disruption.

EERAM Block Diagram
  • 4 Kbit, 16 Kbit I2C
  • Nonvolatile (with small external CVCAP capacitor)
  • Standard symmetrical SRAM reads and writes
  • SRAM reads and writes can be random access or burst
  • Nonvolatile endurance (backups) > 100,000
  • Nonvolatile retention > 100 years
What Problem Does EERAM Solve?

EERAM offers unlimited writes to the SRAM array, allowing you to constantly write to the device. Since power loss events are typically random or unpredictable, EERAM works in applications that absolutely cannot lose the quickly changing SRAM data on any sudden power loss. It provides designers of data logging/black box or monitoring systems with a safe and accurate way to safely, reliably and automatically store the last data bytes prior to the power loss event. The capacitor connected to the VCAP pin provides the necessary energy to safely copy the RAM’s contents to the secure nonvolatile backup on power loss. Upon power-up, data is recalled automatically from the nonvolatile cells to the SRAM.

What Are the Benefits of EERAM?
  • Reliably preserves data through any power loss event
  • Automatically and safely stores data on power loss
  • Restores data automatically to SRAM on each power up
  • No battery needed
  • Unlimited reads and writes to standard serial SRAM memory
    • Write to the memory as often as you choose
    • Read from the memory as often as you choose
    • Writes and Reads can be random access one byte at a time or can be bursts of reads and writes
  • Lowest-cost nonvolatile SRAM solution by using standard CMOS memory cells for both SRAM and nonvolatile
    • Notably less expensive than competing FRAM and nvSRAM technologies
  • Low power consumption
Where is EERAM Used?

EERAM in Smart Meters:

Fast data-writing speedProtects against data loss in the event of a power failure
Read/write cycle endurancePermits data collection at frequent intervals
Back-up via capacitorEliminates the need for a battery back-up to preserve data


EERAM in Automobiles:

ApplicationWhy Is EERAM Needed?
AirbagCollects and stores info every second – blackbox
Telematics/NavigationStores navigation waypoints, bookmarks, etc. for user data at ignition on
EntertainmentCaptures and holds changing station information so available at ignition on
Instrument ClusterTracks elapsed miles
Tire PressureTire pressure logs (data logger)
ABS - Stability ControlHolds data from ABS sensors – information such as speed, turn radius and wheel rotation
Power TrainAdaptive system that manages the power train constantly; writes data to memory