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Designers of electric meters face the ongoing challenge of keeping system costs down. If the record-keeping portion of a system is tampered with, revenues collected from the end customer could be drastically reduced. To prevent the loss of billing data in the event of a power failure, this data is stored regularly into nonvolatile memory as often as once a minute or 525,600 writes per year. This means that a high-endurance memory such as an EEPROM or serial SRAM and a real-time clock that is accurate over temperature are required.

For reliable code and data storage, we offer a broad range of NOR Flash memory products including Parallel Flash, SPI, and Serial Quad I/O™ (SQI™). Supporting a variety of densities that can operate over wide voltage and temperature ranges and available in very small packages, these devices can meet the requirements of any metering application. SuperFlash® memory devices are cost-effective, nonvolatile memory data storage solutions that combine industry-leading features  with fixed and fast program/erase times, ultra-low power consumption, high endurance and excellent reliability.

Serial EERAM is an easy, low-power and low-cost solution for implementing data logging and tamper detection in electric meters.

Key Features


Memory Products

  • High-endurance serial EEPROM up to 1M erase/write cycles
  • I²C or SPI serial interface
  • Industry-leading reliability
  • Wide operating voltage and temperature
  • SPI serial SRAM has unlimited endurance
  • SRAM available in small 8-pin package

SuperFlash Memory Products

  • 100 years data retention (JEDEC standard A103)
  • 100K endurance (JEDEC standard A117)
  • Small sector architecture
  • Fastest and fixed erase/program times
  • Ultra-low power consumption for battery-operated applications
  • Execute-In-Place (XIP) capability with low latency
  • Support for high frequency/bandwidth
  • Cutting-edge micro-packages available

Real-Time Clock/Calendars

  • Current as low as 700 nA max.
  • Operate to 1.3V
  • Battery switchover for backup power (Vbat)
  • Timestamps at power fail and restore
  • Wide digital trimming range
  • Event Detect input with switch debounce
  • Watchdog timer
  • I²C or SPI serial interface available

Memory Technology


High-Endurance Serial EEPROM and Serial SRAM Memory

Since data storage is a critical factor, a reliable memory such as a serial EEPROM has been the industry preference for many years. Our 24xxx and 25xxx serial EEPROM devices support an I²C and SPI serial interface respectively.

Flash Memory

For applications with higher- density memory requirements, our NOR Flash memory products with patented and proprietary SuperFlash nonvolatile Flash memory cells are an ideal solution. SuperFlash memory uses a split-gate cell design and a thick-oxide tunneling injector to offer you significant cost and reliability benefits. Superior reliability of 100,000 cycles endurance and greater than 100 years of data retention ensures robust and reliable designs for meter applications. Small sector architecture enables a system to choose the right amount of data/code to be erased to update contents, allowing seamless partition of program and data code to occupy less memory space.

We offer multiple interfaces to satisfy different design needs. Parallel Flash offers asynchronous random access through a dedicated address bus. SQI Flash memory reads and writes through a 4-bit multiplexed synchronous serial communication interface to enable  low-pin-count, high-bandwidth code Execute-in-Place (XIP) applications. SPI Flash is a cost-effective option to store the bootloader code, making it available for downloading into shadow memory upon power up.

Memory Cell Structure

  • No over-erase problem
  • Low total power consumption during erase
  • Low leakage current during erase
  • Small sector architecture
  • Faster re-write times

Real-Time Clock/Calendar (RTCC) Technology


I2C RTCC

SPI RTCC

Integration

The MCP794xx and MCP795xxx low-power RTCC devices feature nonvolatile memory and can operate down to 1.3V through the backup supply connected to the VBAT input for timekeeping and SRAM retention only. As part of the power sense circuit, a time saver function is implemented to store the time when main power is lost and again when power is restored to log the time and duration of any power failure. A Watchdog Timer (WDT) is included for applications outside the microcontroller (MCU).

Accuracy

Accuracy is needed over a wide temperature range. These RTCC devices were implemented with digital trimming to support a software temperature-compensated design. In a design that uses an MCU and an external temperature sensor, the digital trimming registers can be updated with new calibration parameters when the temperature changes.

Unique ID

A 64-bit or 128-bit protected EEPROM space is available for a unique ID or MAC address to be programmed at the factory or by the end user.

Anti-Tamper

To support anti-tampering requirements, two types of digital event detects are available in the MCP795xxx RTCC. One event detect input is high speed with a programmable pulse count that can identify the 1/4/16/32 pulses before sending an interrupt the MCU. The second event detect is low speed with a built-in debounce input filter to support noisy mechanical switches or the removal of a panel from the meter. Since the RTC is running all the time, the event detects operate all the time.