EEPROMs for smart meters

Key Feature 1 | Key Feature 2 Lineup

ROHM High Reliability Memory for Smart Meters

Overview

Smart meters are key devices in the configuration of smart grids, which are quickly proliferating due to their greater energy savings, fixed fee setting capability, stable power supply, power theft countermeasures, and improved power selling functionality.
ROHM offers a variety of semiconductor products optimized for smart meters.
As the world's 3rd* largest supplier of high reliability EEPROMs, ROHM utilizes original double cell construction and double reset functionality that result in zero accidental failures.
Three series are available, based on bus type:
1) I2C bus, featuring low power consumption and high speed operation (BR25S Series: 8kbit-256kbit)
2) SPI bus (BR25S Series: 32kbit-2556kbit)
3) Microwire bus (BR93L Series: 1kbit-16kbit)

*January 2010 ROHM survey

Key Feature 1 : Failsafe double cell structure + Double reset function

Double Cell / Double Reset

■ Double Cell

Data is written to the EEPROM by passing electrons through a tunnel-oxide film. This process places a significant amount of stress on the film, which can lead to erosion and, subsequently, memory bit failures that can prevent data from being written to the cells.
To avoid this, ROHM utilizes a unique double-cell structure that allocates two cells for each bit of data. Therefore, if one cell malfunctions the other will automatically activate for seamless operation.

Double Cell

■ Double Reset

Typically, ICs are unstable during ON/OFF. Often, noise is generated, which can lead to microcontroller malfunctions. Opamps and general logic ICs can normally recover from malfunctions. EEPROMs, on the other hand, are highly susceptible to memory failure, even after one malfunction. ROHM EEPROMs resolve this problem by utilizing two protection circuits (power ON reset/undervoltage erroneous WRITE detection) that prevent malfunctions due to power failures and ON/OFF switching.

Double Reset

Key Feature 2 : Safe, uniform production

  • A streamlined, uniform manufacturing process, from wafer production to assembly, results in unsurpassed quality
    In addition, wafer fabrication and package assembly locations are dispersed, hedging risk
  • Data writing services are also performed, and high reliability products are delivered with a short turnaround time

Lineup

■ I2C BUS BR24SSeries(8kbit to 256kbit)

  • 100% compatible with the universally standard I2C bus. Complete control is possible using just 2 ports: Serial Clock (SCL) and Serial Data (SDA)
  • Devices other than EEPROMs can be connected to the same ports, making it possible to save microcontroller ports
  • 1.7V to 5.5V single power supply operation
  • High-speed Page Write mode
Part No. I/F Capacity
(Bit)
Bit
Structure
(Word to Bit)
Operating
Voltage
Range
(V)
Operating
Temperature
Range
(ºC)
Write
Cycle
Time
(max.)(ms)
Rewrite
Frequency
(Times)
Data
Storage
(Year)
RoHS
Compliance
BR24S08 I2C BUS 8K 1K to 8 1.7 to 5.5 -40 to +85 5 106 40 Yes
BR24S16 I2C BUS 16K 2K to 8 1.7 to 5.5 -40 to +85 5 106 40 Yes
BR24S32 I2C BUS 32K 4K to 8 1.7 to 5.5 -40 to +85 5 106 40 Yes
BR24S64 I2C BUS 64K 8K to 8 1.7 to 5.5 -40 to +85 5 106 40 Yes
BR24S128 I2C BUS 128K 16384 to 8 1.7 to 5.5 -40 to +85 5 106 40 Yes
BR24S256 I2C BUS 256K 32768 to 8 1.7 to 5.5 -40 to +85 5 106 40 Yes

■ SPI BUS BR25SSeries(32kbit to 256kbit)

  • High-speed (20MHz max.) clock operation
  • Wait Function based on the Hold B terminal
  • Enables designation of certain blocks (or all blocks) for read only (ROM), preventing rewriting, depending on the program.
  • High-speed Page Write mode
Part No. I/F Capacity
(Bit)
Bit
Structure
(Word to Bit)
Operating
Voltage
Range
(V)
Operating
Temperature
Range
(ºC)
Write
Cycle
Time
(max.)
(ms)
Rewrite
Frequency
(Times)
Data Storage
(Year)
RoHS
Compliance
BR25S320 SPI BUS 32K 4K to 8 1.7 to 5.5 -40 to +85 5 106 40 Yes
BR25S640 SPI BUS 64K 8K to 8 1.7 to 5.5 -40 to +85 5 106 40 Yes
BR25S128 SPI BUS 128K 16384 to 8 1.7 to 5.5 -40 to +85 5 106 40 Yes
BR25S256 SPI BUS 256K 32768 to 8 1.7 to 5.5 -40 to +85 5 106 40 Yes

■ Microwire BUS BR93LSeries(1kbit to 16kbit)

  • 3-line communication (Chip Select, Serial Clock, Serial Data) utilized for common input/output tasks.
  • Supports high-speed clock operation (2MHz max.)
  • High-speed writing (5ms max.)
  • Common package and pin layout (for 1kbit-16kbit products) ensure support for software modifications.
  • 1.8V-5.5V single power supply operation
Part No. I/F Capacity (Bit) Bit
Structure
(Word to Bit)
Operating
Voltage
Range
(V)
Operating
Temperature
Range
(ºC)
Write
Cycle
Time
(max.)
(ms)
Rewrite
Frequency
(Times)
Data
Storage
(Year)
RoHS
Compliance
BR93L46 Microwire BUS 1K 64 to 16 1.8 to 5.5 -40 to +85 5 106 40 Yes
BR93L56 Microwire BUS 2K 128 to 16 1.8 to 5.5 -40 to +85 5 106 40 Yes
BR93L66 Microwire BUS 4K 256 to 16 1.8 to 5.5 -40 to +85 5 106 40 Yes
BR93L76 Microwire BUS 8K 512 to 16 1.8 to 5.5 -40 to +85 5 106 40 Yes
BR93L86 Microwire BUS 16K 1K to 16 1.8 to 5.5 -40 to +85 5 106 40 Yes