Ferroelectric random access memory (FRAM) memory is widely used in industrial control systems, industrial automation, mission-critical space applications, high-reliability military, and various automotive applications. The characteristics of FRAM that make it suitable for these applications also make FRAM a viable technology for smart e-meter applications because of its additional inherent attributes, those being low power and high endurance. Figure 1 below is comparison of typical high-level non-volatile memory attributes.
Fig. 1: High-Level Non-Volatile Memory Comparison
A major consideration for electronic designs concerns reducing total power consumption while increasing reliability. Designers must add functionality while simultaneously shrinking the system's power budget to achieve longer battery life. At the same time, however, embedded software is becoming more complex, requiring more memory and thus further stressing the power budget.
Typically, smart e-meters store billing and usage data in secure NV memories. FRAMs serve this role well due to their excellent tamper-proof nature and cell structure that prevents unauthorized data reads. Traditional memory types store data as an electrical charge that vulnerable to tampering by unauthorized elements by scanning. FRAM stores data as a polarization state and thus has less exposure to and risk of tampering.
FRAM offers several real advantages compared to other non-volatile memory types
- Real-time data storage with no write-delays or soak time: EEPROMs and NOR Flash have a write delay (5ms to 10ms) and associated page-writes which prevent byte writing of data. In scenarios needing instant logging of billing information or critical time stamping information, FRAMs are faster than any other non-volatile memory type.
- Almost infinite endurance: For example, Cypress' FRAMS offer 100-trillion write cycle endurance. Such high endurance is usually useful for systems with frequent writes. As the pattern to store the "interval data" (user's usage of electrical power, peak power considerations, billing information) becomes more frequent and designs become complex – wear leveling can add an aspect of difficulty in system designs.
- Low energy to write: As shown in Figure 1, the instantaneous write and low active write current of FRAM simplify elongating operating life for systems running on a battery.
- Secure and reliable data storage: Billing information is one of the most critical pieces of information store in non-volatile memory. For example, electricity providers worldwide have the most conflicts when it comes to "Quality of Service" (QoS) with regards to authenticity of billing. FRAM has inherent advantages when it comes to secure data-storage and offers flexibility and simplicity over Flash- or EEPROM-based designs.
Fig. 2: Typical Block Diagram of an e-meter
FRAM can lower system cost, increase system efficiency, and reduce complexity while being significantly lower power than NOR Flash, EEPROMs, battery-backed traditional SRAMs, and other comparable technologies.
About the Author
Harsha Venkatesh has been working with the Cypress Memory team for the past four years, mainly in the Specialty Memories group. Harsha holds a Masters in Business Administration from National Institute of Industrial Engineering, Mumbai, and currently handles Memory Marketing for Central Europe.