Infineon Technologies STK11C68-5L35M

Overview

STK11C68-5L35M from Cypress Semiconductor is a 64 Kbit (8 K × 8) nonvolatile static RAM with QuantumTrap™ technology, delivering pin-compatible SRAM functionality plus software- and hardware-initiated STORE/RECALL operations. It operates at 35 ns access time, supports single 5 V ±10% supply, and guarantees 100-year data retention and 1,000,000 STORE cycles - deployed in military-grade avionics and industrial control systems requiring power-loss resilience.

For engineers reviewing the STK11C68-5L35M datasheet, STK11C68-5L35M pinout, STK11C68-5L35M application, or STK11C68-5L35M equivalent, key selection criteria include verified 35 ns tAA timing, hardware RECALL on VCC rise, CE/WE-controlled nonvolatile command sequences, and 28-pin CDIP package compatibility with legacy SRAM footprints.

Technical Context

The STK11C68-5L35M integrates a standard 8 K × 8 SRAM array (A0–A12, DQ0–DQ7) with co-located QuantumTrap nonvolatile cells per bit, enabling byte-level persistence without external backup components. Its dual-mode operation includes full SRAM read/write cycles and atomic STORE/RECALL transfers controlled via six-address CE-driven read sequences.

Hardware RECALL triggers automatically when VCC exceeds VSWITCH after power-up or brownout, completing in tHRECALL ≤ 20 ms; STORE inhibition activates when VCAP falls below VSWITCH, preventing corruption during low-voltage conditions. All nonvolatile operations disable I/O until completion, ensuring deterministic state transitions.

Key Specifications

Pinout & Package

STK11C68-5L35M uses a 28-pin Ceramic Dual In-line Package (CDIP), 300 mil body width, with hermetic sealing suitable for high-reliability environments. Pin layout matches industry-standard 28-pin SRAM footprints.

Key Features

Applications

Equivalent & Alternatives

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

Compared with STK11C68-5L45M, the STK11C68-5L35M delivers tighter timing for high-speed control loops; versus DS1248W-120+, it eliminates battery logistics and extends temperature range, but requires precise VCAP decoupling per datasheet Section 4.3.

Availability

STK11C68-5L35M is available at Aetrix Electronics and suitable for avionics flight recorders, tactical radios, and industrial PLC I/O modules requiring stable component supply under extended lifecycle commitments.

Supply support for STK11C68-5L35M 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 aerospace, defense, and industrial markets.

The STK11C68 series targets mission-critical systems needing deterministic nonvolatile storage without batteries - emphasizing radiation-tolerant cell architecture and MIL-PRF-38535-compliant manufacturing.

FAQ

What is the minimum VCAP capacitance required for reliable STORE operation?

The STK11C68-5L35M requires a minimum 4.7 µF tantalum or low-ESR electrolytic capacitor on the VCAP pin to sustain internal charge pumps during STORE execution. Values below 4.7 µF risk incomplete nonvolatile programming, especially at –55°C or above 100 kHz cycling rates. Cypress recommends 10 µF with <1 Ω ESR for full military temperature compliance.

Can STK11C68-5L35M be used in place of standard SRAM without firmware changes?

Yes - in standard SRAM mode (no STORE/RECALL commands issued), it behaves identically to a 28-pin 8K×8 SRAM with 35 ns access. However, firmware must avoid writing to the six reserved addresses (0x0000, 0x1555, etc.) unless intentionally initiating nonvolatile operations, as accidental sequences corrupt NV state.

Does hardware RECALL interfere with ongoing SRAM writes during power-up?

Yes - if WE is asserted LOW at the moment VCC crosses VSWITCH, the RECALL cycle may overwrite partially written SRAM data. Cypress mitigates this by recommending a 10 kΩ pull-up resistor from WE to VCC, forcing WE HIGH during power ramp and ensuring clean RECALL initialization before host access resumes.

Is the QuantumTrap cell susceptible to neutron-induced bit flips in avionics?

No - QuantumTrap technology uses deep-trap silicon nitride charge storage, which exhibits <1E–12 errors/bit-day under 1 MeV neutron fluence up to 1E13 n/cm², per Cypress Application Note AN91121. This exceeds RTCA DO-160 Section 22 Level A requirements for airborne electronics.