FM33256 – FRAM-Enhancedâ„¢ Processor Companion with high-speed SPI interface


This integrated, single-chip solution replaces discrete components to reduce board space and cost in processor-based metering systems.  

The FM33256 combines 256 kilobits of FRAM with a high-speed serial peripheral interface (SPI), leveraging FRAM’s high-speed write capability. 

The device includes a real-time clock/calendar/alarm (RTC) that draws less than 1 micro amp and can be battery-backed or capacitor-backed with no additional circuits (i.e. battery crossover, capacitor charging circuit).  Other features of the FM33256 include a programmable low-VDD reset, a programmable watchdog timer, a manual reset function, a nonvolatile event counter, a lockable serial number, and a general-purpose comparator that can be used for early warning power-fail interrupts (NMI). 

The device operates from 2.7 to 3.6 volts over the entire industrial temperature range (-40 degrees C to +85 degrees C) and is available in a green 14-pin SOIC package.  
FRAM offers three distinct benefits in advanced metering designs:

  • No Delay™ reads/writes:  FRAM writes data at bus speed, eliminating the need for a complicated data backup system in the event of power loss.
  • Virtually unlimited endurance:  FRAM collects data for an unlimited period without wearing out.  In an electric meter FRAM can be written every second for the life of a meter.  No other nonvolatile memory offers this capability.  Less advanced designs that exclude FRAM can only afford to write the data when power is failing because alternative memory products wear out quickly if they are written too often.
  • Low power consumption:  FRAM devices are RAMs and do not require charge pumps and are, therefore, orders of magnitude lower in power during write cycles than floating gate devices such as flash and EEPROM.  During battery-powered data collection, FRAM devices offer the lowest power operation of any memory solution available, making them ideal for a variety of data collection applications including water and gas meters.