Infineon Technologies STK12C68-SF45

Overview

STK12C68-SF45 from Cypress Semiconductor is a 64 Kbit (8 K × 8) nonvolatile SRAM with QuantumTrap technology, delivering 45 ns access time, AutoStore on power-down using an external 68 µF capacitor, and unlimited SRAM read/write cycles. It operates at single 5 V ±10%, supports software/hardware STORE/RECALL, and is used in industrial control systems requiring persistent memory without battery backup.

For engineers reviewing the STK12C68-SF45 datasheet, STK12C68-SF45 pinout, STK12C68-SF45 application, or STK12C68-SF45 equivalent, key selection criteria include AutoStore timing behavior, HSB-controlled hardware store latency, VCAP capacitor sizing for reliable power-loss store, and compatibility with legacy 28-pin SOIC-based memory interfaces in embedded controllers and data loggers.

Technical Context

The STK12C68-SF45 integrates parallel SRAM and QuantumTrap nonvolatile cells per bit, enabling simultaneous STORE/RECALL of all 8,192 bytes. Its architecture decouples volatile operation from nonvolatile persistence: SRAM delivers standard fast random access, while STORE to QuantumTrap occurs automatically at VCC drop below VSWITCH (~3.6 V), triggered by internal charge pump and VCAP discharge.

STORE initiation is conditional-only executed if at least one SRAM write occurred since last STORE/RECALL. Hardware STORE uses the open-drain HSB pin with tDELAY timing (≥100 ns), while software STORE relies on a six-address CE-controlled read sequence (0x0000 → 0x0F0F). RECALL on power-up completes in tHRECALL ≤ 12 ms.

Key Specifications

Pinout & Package

STK12C68-SF45 is packaged in a 28-pin SOIC (330 mil width), pin-compatible with industry-standard 28-pin SRAM footprints. The package supports surface-mount reflow and hand-soldering with JEDEC MS-012AC compliance.

Key Features

Applications

Equivalent & Alternatives

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

Compared with CY14B108L-ZSP25XI and FM1808-40-TG, STK12C68-SF45 offers direct 28-pin SOIC replacement for legacy SRAM designs, deterministic AutoStore timing tied to VCC slope, and minimal firmware changes - making it optimal for cost-sensitive industrial retrofits where pin compatibility and known timing behavior are critical.

Availability

STK12C68-SF45 is available at Aetrix Electronics and suitable for industrial PLCs, medical infusion devices, and telecom line cards requiring stable component supply with long-term lifecycle assurance.

Supply support for STK12C68-SF45 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) is a fabless semiconductor company specializing in memory, microcontrollers, and connectivity solutions for industrial, automotive, and consumer applications.

The STK12C68 belongs to Cypress's QuantumTrap nvSRAM product line, designed specifically to replace battery-backed SRAM in mission-critical systems where maintenance-free, long-retention, and deterministic power-loss data capture are mandatory.

FAQ

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

The STK12C68-SF45 requires a minimum 68 µF tantalum or polymer capacitor rated at 6 V with ±20% tolerance on the VCAP pin. Lower values risk incomplete STORE under fast VCC droop or elevated temperature; 100 µF is recommended for margin in industrial environments with >10 ms brown-out duration.

Can STK12C68-SF45 operate without the VCAP capacitor?

Yes - in AutoStore Inhibit mode, VCC is grounded and +5 V is applied directly to VCAP, disabling automatic power-loss store. STORE then requires explicit software or HSB initiation. This mode removes capacitor aging concerns but forfeits hands-off data protection during uncontrolled power loss.

How does the HSB pin behave during a software-initiated STORE?

HSB goes LOW at the start of any STORE operation - including software-initiated ones - and remains LOW for the full tSTORE duration (≤10 ms). It returns HIGH only after the QuantumTrap programming completes and SRAM is re-enabled, providing unambiguous hardware synchronization for host processors.

Is STK12C68-SF45 compatible with 3.3 V I/O systems?

No - STK12C68-SF45 is strictly a 5 V ±10% device. Its inputs are not 5 V tolerant in 3.3 V mode, and VCC must be ≥4.5 V for valid operation. Interfacing with 3.3 V controllers requires level-shifting on all address, data, and control lines, or selecting a native 3.3 V nvSRAM like the CY14B101Q.