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Preliminary
FM31T372/374/376/378
System Supervisor & Temperature Compensated RTC
(TCXO) with Embedded Crystal
Features
High Integration Device Replaces Multiple Parts
Real-time Clock (RTC)
o Embedded 32.768kHz Crystal
o Temperature Compensated
32.768 kHz Clock Output
Low-VDD Detection Drives Reset
Watchdog Timer
Early Power-Fail Warning/NMI
Two 16-bit Event Counters with Event Driven
Interrupt Output
Serial Number with Write-lock for Security
Ferroelectric Nonvolatile RAM
4Kb, 16Kb, 64Kb, and 256Kb versions
Unlimited Read/Write Endurance
10 year Data Retention
NoDelay™ Writes
Real-time Clock/Calendar
Temp-Compensated Using On-Chip Sensor
o 5 ppm over -40°C to +85°C
o Accuracy 2 ½ min. per year
Backup Current 1.4 A (max.) at +25C
Seconds through Centuries in BCD format
Tracks Leap Years through 2099
No External Crystal Required
Offset Register to Correct for Crystal Aging
Supports Battery or Capacitor Backup
Processor Companion
32.768 kHz Clock Output
Active-low Reset Output for VDD and Watchdog
Programmable VDD Reset Trip Point
Manual Reset Filtered and Debounced
Programmable Watchdog Timer
Dual Battery-backed Event Counter Tracks
System Intrusions or other Events
Event Counter Driven Interrupt Output
Comparator for Early Power-Fail Interrupt
64-bit Programmable Serial Number with Lock
Fast Two-wire Serial Interface
Up to 1 MHz Maximum Bus Frequency
Supports Legacy Timing for 100 kHz & 400 kHz
Device Select Pins for up to 4 Memory Devices
RTC, Supervisor Controlled via 2-wire Interface
Easy to Use Configurations
Operates from 2.7 to 5.5V
Small Footprint 14-pin “Green” SOIC (-G)
Low Operating Current
-40C to +85C Operation
Description
The FM31T37x is a family of integrated devices that
includes the most commonly needed functions for
processor-based systems. Major features include
nonvolatile F-RAM memory available in various
sizes, temperature-compensated real-time clock with
embedded crystal, 32.768kHz clock output,
low-VDD reset, watchdog timer, battery backed
event counter, event driven interrupt output, lockable
64-bit serial number area, general purpose
comparator that can be used for an early power-fail
(NMI) interrupt or other purpose, and 2-wire serial
interface to a host microcontroller. The family
operates from 2.7 to 5.5V.
The real-time clock (RTC) provides time and date
information in BCD format. It can be permanently
powered from external backup voltage source, either
a battery or a capacitor. The timekeeper uses an
internal 32.768 kHz crystal which is factory-
calibrated for excellent timekeeping accuracy over
the industrial temperature range.
This is a product that has fixed target specifications but are subject
to change pending characterization results.
Rev. 1.1
Apr. 2011
The FM31T37x devices integrate 4Kb, 16Kb, 64Kb,
and 256Kb of F-RAM memory. F-RAM offers
superior write speed and unlimited endurance. This
allows the memory to provide system data collection
and as read/write RAM storage. This memory is truly
nonvolatile rather than battery-backed.
The processor companion includes commonly needed
CPU support functions. Supervisory functions
include a reset output signal controlled by either a
low VDD condition or a watchdog timeout. /RST
goes active when VDD drops below a programmable
threshold and remains active for 100 ms after VDD
rises above the trip point. A programmable watchdog
timer runs from 100 ms to 3 seconds. The watchdog
timer is optional, but if enabled it will assert the reset
signal for 100 ms if not restarted by the host before
the timeout. A flag-bit indicates the source of the
reset.
Ramtron International Corporation
1850 Ramtron Drive, Colorado Springs, CO 80921
(800) 545-FRAM, (719) 481-7000
http://www.ramtron.com
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