Companions mop up system functions with FRAM

A novel FRAM-based processor companion family features highly integrated support and peripheral functions for processor-based systems.

A novel FRAM-based processor companion family features highly integrated support and peripheral functions for processor-based systems.

The FM3104, FM3116, FM3164 and FM31256 devices combine a nonvolatile ferroelectric RAM with a real-time clock, a processor supervisor and additional peripheral functions.

Ramtron's processor companion family, its most integrated FRAM product developed to date, provides commonly needed system functions for a variety of automotive, consumer, communications, industrial, metering and computing applications.

The FM31X processor companion family includes a processor supervisor that features a programmable low-voltage reset, a programmable watchdog timer and a manual reset function.

Additional peripherals include a nonvolatile event counter, a lockable 64bit serial number area, and a general purpose comparator that can be used for an early power-fail interrupt or other purpose.

Implementing these complementary but distinct functions using an advanced 0.35-micron manufacturing process allows them to share a common interface and combine to fit in a tiny 14-pin SOIC package, replacing the need for multiple parts on a system board.

An industry standard two-wire bus is used to access the memory and control all functions.

All devices operate from 2.7 to 5.5V and are available in 4, 16, 64 and 256Kbit densities.

"No other processor support chip has the unique nonvolatile memory features of unlimited endurance and fast read/write", stated Mike Alwais, VP FRAM products of Ramtron International.

"The processor companion family also gives system designers the most highly integrated system management solution to support virtually any microcontroller- or microprocessor-based design".

"Through the careful integration of nonvolatile memory, all individual features are improved versus discreet versions and the total package achieves superior bill of material cost and board space", he said.

Each device incorporates a processor supervisor that provides a host processor with two basic functions: detection of power supply fault conditions and a watchdog timer to escape a software lockup condition.

A reset pin drives the processor-reset input during power faults, power-up and -down, and software lockups.

The reset pin also provided a switch debounce function to facilitate manual reset inputs.

An early power fail warning can be provided to the processor well before VDD drops out of specification.

The comparator is used to create a power fail interrupt.

This is ideal for saving critical data in nonvolatile FRAM.

A separate memory location to write a 64bit serial number is provided.

It is a writeable nonvolatile memory block that can be locked by the user once the serial number is set.

Once locked, the serial number cannot be altered.

The real-time clock can be battery or capacitor backed for permanently powered operation.

It offers a software calibration feature that provides high accuracy.

Each device offers the user two battery-backed event counters, which are 16bit each, cascading to one 32bit counter, including a programmable edge detect.

This unique counter can be used to log system intrusions (tamper events) or virtually any other general-purpose event.

The real-time clock/calendar is intended to be permanently powered.

When the primary system power fails, the voltage on the VDD pin will drop.

When VDD is less 2.5V the RTC (and event counters) will switch to the backup power supply.

The backup source can be either a battery or capacitor.

A trickle charger facilitates capacitor backup.

The backup voltage pin can optionally provide a trickle charge current.

Data are nonvolatile, and so will not be lost if the capacitor fails.

The processor companion family comes with options of 4, 16, 64 or 256Kbit of nonvolatile FRAM.

FRAM technology replaces system SRAM or nonvolatile memory as it reads and writes at bus speed with no delay and offers unlimited write cycles.

Samples are available for the FM3104, FM3116, FM3164 and FM31256 in a 14-pin SOIC package with prices starting at $2.04 for 4Kbit, $2.34 for 16Kbit, $2.75 for 64Kbit and $3.76 for 256Kbit for 10,000-piece quantities.

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