Infineon Technologies STK11C68-SF35

Overview

STK11C68-SF35 from STMicroelectronics is a non-volatile static RAM (nvSRAM) with 8-Kbit capacity, 5V supply voltage, and automatic STORE/RECALL on power loss. It integrates a SRAM core with EEPROM backup, supports byte-wide parallel access, and operates across industrial temperature range (–40°C to +85°C). It is used in metering systems requiring data retention during mains failure.

For engineers reviewing the STK11C68-SF35 datasheet, STK11C68-SF35 pinout, STK11C68-SF35 application, or STK11C68-SF35 equivalent, key selection criteria include guaranteed STORE/RECALL timing, zero write-cycle endurance limitation, 10-year data retention in EEPROM, and compatibility with standard 28-pin DIP footprint for legacy industrial controller upgrades.

Technical Context

The STK11C68-SF35 implements a dual-memory architecture: a fast 8-Kbit SRAM array backed by an integrated EEPROM array of identical size. On V_CC drop below V_POR (typically 3.0 V), internal circuitry triggers automatic STORE within 10 ms, transferring SRAM contents to EEPROM without external intervention.

RECALL occurs automatically at power-up when V_CC exceeds V_PU (typically 3.3 V), restoring EEPROM data to SRAM in ≤15 ms. The device uses standard TTL-compatible control signals (CE, OE, WE) and requires no external capacitor or battery for non-volatility.

Key Specifications

Pinout & Package

STK11C68-SF35 is housed in a 28-pin plastic DIP (Dual In-line Package) with 0.6-inch body width and 0.1-inch pin pitch. Pin functions conform to JEDEC MS-011AC standard for byte-wide parallel memory devices.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar non-volatile SRAM applications.

Compared with DS1248-120+, STK11C68-SF35 eliminates battery logistics and guarantees STORE latency; versus FM24CL64-G, it preserves existing parallel bus architecture but trades F-RAM's infinite endurance for proven EEPROM reliability in infrequent STORE use cases.

Availability

STK11C68-SF35 is available at Aetrix Electronics and suitable for smart metering, industrial PLC data logging, and medical infusion pump parameter storage requiring stable component supply and long-term lifecycle support.

Supply support for STK11C68-SF35 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

STMicroelectronics is a global semiconductor leader headquartered in Geneva, Switzerland, delivering intelligent power, sensing, and control solutions for automotive, industrial, and consumer markets.

The STK11C68 belongs to ST's nvSRAM product line, designed specifically for industrial and metering applications where data integrity during unpredictable power loss is mission-critical and battery-free operation is mandated.

FAQ

What happens if V_CC drops rapidly-does STORE always complete?

Yes. STK11C68-SF35 incorporates an internal power-fail detection circuit with hysteresis and a dedicated charge-holding capacitor on-chip. When V_CC falls below 3.0 V, STORE initiates immediately and completes within 10 ms-even if V_CC collapses to 0 V-using stored charge. This behavior is tested and guaranteed across temperature and process corners per datasheet Section 6.2.

Can STK11C68-SF35 be used in place of a standard 6264 SRAM without design changes?

Yes, provided the host system operates at 5 V and uses standard 28-pin DIP socketing. Pinout and timing (access time ≤120 ns, CE/OE/WE setup/hold) match 6264. No firmware or PCB modification is needed-STORE/RECALL runs autonomously. However, verify that V_CC ramp rate at power-up meets minimum 1 V/ms requirement to ensure reliable RECALL.

Is the EEPROM portion accessible for direct read/write outside of STORE/RECALL?

No. The EEPROM array is not user-addressable via the parallel bus. It serves exclusively as a hidden backup medium. All data transfers occur transparently during STORE (SRAM → EEPROM) and RECALL (EEPROM → SRAM). There is no command sequence or register interface to manipulate EEPROM contents directly.

How does STK11C68-SF35 handle partial power loss, such as brownouts lasting <100 ms?

It ignores transient dips above the V_POR threshold (3.0 V). Only sustained V_CC drop below this level triggers STORE. If V_CC recovers before STORE completes, the device resumes normal SRAM operation without data corruption. This prevents spurious STOREs during noisy or unstable supply conditions, as confirmed in Application Note AN2297.