Infineon Technologies FM31L278-G

Overview

FM31L278-G from Infineon Technologies (formerly Cypress) is a 256-Kbit integrated processor companion IC combining ferroelectric RAM (F-RAM), real-time clock (RTC), low-VDD supervisor, watchdog timer, dual event counter, and 64-bit lockable serial number in a single 14-pin SOIC package. It delivers 10¹⁴ write endurance, 151-year data retention, 1.15 µA RTC backup current at 2 V, and supports I²C up to 1 MHz for industrial metering and embedded control systems.

For engineers reviewing the FM31L278-G datasheet, FM31L278-G pinout, FM31L278-G application, or FM31L278-G equivalent, key selection criteria include F-RAM write endurance vs. EEPROM, battery-backed RTC/calendar with leap-year support through 2099, programmable VDD reset threshold, dual edge-triggered event counters, and I²C address select pins enabling up to four devices on one bus.

Technical Context

The FM31L278-G implements two logically independent I²C slave interfaces: one for the 32K × 8 F-RAM array (standard memory device ID), and another for the companion function block (RTC, supervisor, counters, serial number) using dedicated special-function registers. This separation allows concurrent memory access and timekeeping updates without address pointer interference.

Its RTC operates from VBAK backup power (battery or capacitor), maintaining BCD-formatted time/date including leap years through 2099, with software calibration via CAL/PFO 512 Hz output. The supervisor integrates a comparator referenced to 1.2 V for early power-fail detection (PFI), programmable watchdog timeout (100 ms–3 s), and active-low open-drain RST with 100 ms minimum pulse width after VDD recovery.

Key Specifications

Pinout & Package

FM31L278-G is housed in a 14-pin small outline integrated circuit (SOIC) package with standard 1.27 mm pitch, JEDEC MS-012AC compliant, RoHS and UL recognized.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar integrated processor companion applications.

Compared with DS3231M+ and STM32H743VI, FM31L278-G uniquely consolidates F-RAM endurance, RTC, supervisor, dual counters, and secure serial number in one UL-recognized, RoHS-compliant SOIC - reducing design risk, validation effort, and long-term field reliability concerns in safety-critical industrial deployments.

Availability

FM31L278-G is available at Aetrix Electronics and suitable for smart metering, industrial PLCs, medical infusion pumps, and building energy management systems requiring stable component supply, long-life data retention, and battery-backed timekeeping integrity.

Supply support for FM31L278-G includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Infineon Technologies is a global semiconductor leader headquartered in Munich, Germany, delivering power management, sensing, connectivity, and security solutions for automotive, industrial, and IoT applications.

The FM31L278-G belongs to Infineon's legacy Cypress processor companion family, designed specifically to replace discrete RTC, supervisor, EEPROM, and counter ICs in resource-constrained embedded systems requiring high-reliability nonvolatile storage and timekeeping.

FAQ

What backup power sources are supported for VBAK?

The FM31L278-G supports either a 3 V lithium coin cell (e.g., CR2032) or a large-value tantalum or supercapacitor on VBAK. The integrated trickle charger is UL recognized and limits charging current to safe levels for lithium batteries. If no backup is used, VBAK must be tied to ground and the VBC bit cleared in RTC register 0Bh to disable charging.

How does the dual event counter operate during main power loss?

When VDD drops below operating range, the FM31L278-G automatically switches CNT1 and CNT2 counting circuits to VBAK power. Edge detection remains fully functional, and counts are retained in battery-backed registers. Counts persist across VDD outages and are readable immediately upon VDD restoration via I²C, with no initialization delay or data reload required.

Can the F-RAM and RTC/companion functions be accessed simultaneously?

Yes - the FM31L278-G presents two independent I²C slave addresses: one for the F-RAM array (default 0x50) and another for the RTC/companion registers (default 0x68). This allows a host controller to read time while writing sensor data to F-RAM without address pointer conflict or transaction blocking, enabling true concurrent operation.

Is the 64-bit serial number truly write-locked after programming?

Yes - once the LOCK bit (bit 7 of register 0Ah) is set, the 64-bit serial number area becomes permanently read-only. No subsequent I²C command can modify its contents, even with VBAK or VDD applied. This hardware-enforced lock provides cryptographic-grade uniqueness and tamper resistance for device identity and firmware binding.