Infineon Technologies FM31256-G

Overview

FM31256-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 read/write endurance, 151-year data retention, and NoDelay™ writes, enabling reliable time-stamped logging in industrial metering systems.

For engineers reviewing the FM31256-G datasheet, FM31256-G pinout, FM31256-G application, or FM31256-G equivalent, key selection criteria include I²C-compatible 1-MHz interface timing, battery-backed RTC with software calibration, programmable VDD reset threshold (2.55 V / 2.75 V / 2.95 V / 3.15 V), dual edge-triggered event counters, and F-RAM's absence of write-cycle delays or wear leveling overhead.

Technical Context

The FM31256-G implements two logically independent I²C slave devices on one die: a 32K × 8 F-RAM array (slave address 0x50–0x53) and a companion peripheral block (slave address 0x68) containing RTC registers, supervisor control bits, event counter latches, and serial number fields. All timekeeping and supervision functions remain active under VBAK backup power (2.0–3.6 V).

Its RTC operates in BCD format with leap-year compensation through 2099, uses an external 32.768 kHz crystal (6 pF load), and supports ±1 ppm software calibration via CAL/PFO output. The supervisor includes a programmable watchdog (100 ms–3 s), early power-fail comparator referenced to 1.2 V, and RST output with 100 ms minimum pulse width after VDD recovery.

Key Specifications

Pinout & Package

FM31256-G is housed in a 14-pin small outline integrated circuit (SOIC) package with standard 1.27 mm pitch and RoHS-compliant finish.

Key Features

Applications

Equivalent & Alternatives

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

Compared with DS3231M+ and MAX31328, FM31256-G uniquely combines 256 Kbit F-RAM, dual battery-backed event counters, and lockable serial number in one device - reducing BOM count and PCB area while enabling end-to-end secure, time-stamped data integrity without external support components.

Availability

FM31256-G is available at Aetrix Electronics and suitable for smart metering, industrial data loggers, medical devices, and building automation systems requiring stable component supply, long-term data retention, and robust power-fail resilience.

Supply support for FM31256-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, specializing in power management, sensing, connectivity, and security solutions for automotive, industrial, and IoT applications.

The FM31256-G belongs to Infineon's integrated processor companion product line, designed to replace discrete RTC, supervisor, and nonvolatile memory components in resource-constrained embedded systems requiring high reliability and long service life.

FAQ

What is the maximum I²C clock frequency supported by FM31256-G?

The FM31256-G supports I²C communication up to 1 MHz, with full backward compatibility for legacy 100 kHz and 400 kHz timing. This allows high-speed F-RAM writes while maintaining interoperability with existing controllers that do not support fast-mode plus. The SDA and SCL inputs include Schmitt triggers for noise immunity, and the SDA driver incorporates slope control to reduce EMI.

How does the FM31256-G handle power transitions between VDD and VBAK?

When VDD drops below the programmed reset threshold, the RTC, event counters, and companion registers automatically switch to VBAK power without interruption. The F-RAM remains accessible until VDD falls below ~1.8 V. Upon VDD restoration, the device resumes normal operation with no initialization required - all timekeeping and counter states are preserved across the transition.

Can the lockable 64-bit serial number be reprogrammed after locking?

No. Once the serial number lock bit (SNL in register 0Bh) is set to '1', the 64-bit serial number field becomes permanently read-only. This one-time programming is enforced by hardware and cannot be reversed, ensuring cryptographic binding of firmware to the physical device for anti-counterfeiting and secure boot applications.

What crystal specifications are required for the FM31256-G RTC?

The FM31256-G requires a standard 32.768 kHz tuning-fork crystal with 6 pF load capacitance and ±20 ppm initial tolerance. The crystal connects between X1 and X2 pins; no external load capacitors are needed. For improved stability over temperature, a TCXO may be substituted by driving X1 with its output and biasing X2 to mid-supply, though this is not required for typical industrial applications.