Infineon Technologies STK11C68-5C35M

Overview

STK11C68-5C35M from Cypress Semiconductor is a 64 Kbit (8 K × 8) nonvolatile static RAM with QuantumTrap technology, delivering 35 ns access time, single 5 V ±10% operation, and automatic power-up RECALL. It functions as a drop-in replacement for standard SRAMs in mission-critical military systems requiring persistent data retention without backup batteries or external capacitors.

For engineers reviewing the STK11C68-5C35M datasheet, STK11C68-5C35M pinout, STK11C68-5C35M application, or STK11C68-5C35M equivalent, key selection criteria include STORE/RECALL control timing, VCAP voltage threshold behavior, hardware protect logic under low-VCC conditions, and compatibility with TTL/CMOS input levels across –55 °C to +125 °C.

Technical Context

The STK11C68-5C35M integrates an 8 K × 8 SRAM array with a mirrored nonvolatile QuantumTrap cell array, enabling software-initiated STORE (1,000,000 cycles) and both hardware- and software-triggered RECALL (unlimited cycles). Its control logic decodes six consecutive CE-controlled reads at specific addresses (0x0000 → 0x0F0F for STORE; 0x0000 → 0x0F0E for RECALL) to initiate nonvolatile operations.

Hardware protection activates when VCAP falls below VSWITCH, disabling STORE and SRAM writes; automatic RECALL triggers on power-up when VCC exceeds VSWITCH after VCC < VRESET. The device supports TTL- and CMOS-level inputs and draws ≤75 mA average active current at 35 ns cycle time.

Key Specifications

Pinout & Package

STK11C68-5C35M is packaged in a 28-pin CDIP (300 mil) with through-hole mounting and military-grade hermetic sealing. Pin layout follows JEDEC MS-011AC standard.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar nonvolatile SRAM applications.

Compared with STK11C68-5C45M, the -5C35M delivers tighter timing margins for high-throughput logging; versus DS1248W-120+, it eliminates battery dependency and simplifies qualification but lacks timekeeping-critical for systems prioritizing long-term reliability over timestamping.

Availability

STK11C68-5C35M is available at Aetrix Electronics and suitable for avionics flight control logging, tactical radio configuration storage, and artillery fire control system calibration requiring stable component supply across extended military procurement cycles.

Supply support for STK11C68-5C35M 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

Cypress Semiconductor (now part of Infineon Technologies) designs high-reliability memory and programmable solutions for automotive, industrial, and defense applications, with global manufacturing and test infrastructure.

The STK11C68 product line was engineered specifically for military and aerospace systems needing battery-free, radiation-tolerant nonvolatile memory with deterministic STORE/RECALL timing and extended temperature operation.

FAQ

What is the role of the VCAP pin, and what capacitor value is required?

The VCAP pin connects to an external capacitor that supplies energy to complete the nonvolatile STORE operation during power interruption. Cypress specifies a 4.7 µF solid tantalum capacitor with ≤100 mΩ ESR, mounted within 1 cm of the VCAP and VSS pins. This capacitor must be charged to ≥4.5 V before STORE initiation and sustains internal programming voltage for tSTORE (max 20 ms).

How does hardware protection prevent STORE corruption during brownout?

Hardware protection monitors VCAP voltage against the internal VSWITCH threshold (~3.5 V). When VCAP drops below VSWITCH, the device disables all STORE commands and SRAM writes-even if valid address sequences are applied-until VCAP recovers. This prevents partial STOREs that could corrupt nonvolatile data or leave SRAM in inconsistent states.

Can STK11C68-5C35M be used in commercial-temperature applications?

Yes-although qualified and screened for –55 °C to +125 °C military operation, the STK11C68-5C35M functions reliably across 0 °C to +70 °C and –40 °C to +85 °C ranges. Its electrical specifications (e.g., 35 ns access, 100-year retention) are guaranteed across the full military range, making it suitable for harsh commercial uses like downhole oilfield tools or railway signaling.

Is there a risk of accidental STORE activation from noise on address/control lines?

No-STORE activation requires six exact CE-controlled reads in strict order at specific addresses (0x0000, 0x1555, 0x0AAA, 0x1FFF, 0x10F0, 0x0F0F), with WE held HIGH throughout. Random noise cannot replicate this precise sequence. Additionally, hardware protection disables STORE if VCAP is below threshold, adding a second layer of immunity against spurious activation.