Infineon Technologies STK12C68-5K35M

Overview

STK12C68-5K35M from Cypress Semiconductor is a 64 Kbit (8K × 8) nonvolatile static RAM with QuantumTrap™ technology, delivering 35 ns access time, single 5V±10% operation, and military-grade temperature range (–55°C to +125°C). It integrates SRAM and nonvolatile storage in each cell, enabling automatic STORE on power loss using an external 68 µF capacitor and software/hardware-initiated RECALL-used in avionics data logging, industrial PLCs, and telecom control memory where power interruption resilience is critical.

For engineers reviewing the STK12C68-5K35M datasheet, STK12C68-5K35M pinout, STK12C68-5K35M application, or STK12C68-5K35M equivalent, key selection considerations include AutoStore timing constraints (10 ms STORE cycle), VCAP capacitor requirements (68–220 µF, 6V), HSB pin behavior during hardware store, and software STORE/RECALL address sequences (e.g., 0x0F0F for STORE initiation).

Technical Context

The STK12C68-5K35M implements a dual-cell architecture: a standard fast SRAM array (128 × 512) paired with parallel QuantumTrap nonvolatile elements. STORE transfers data from SRAM to nonvolatile cells under three triggers-power-down AutoStore, HSB-driven hardware store, or six-address software sequence-while RECALL restores data at power-up or via software (0x0F0E).

Operation is governed by strict voltage thresholds: VSWITCH (~3.6V) disables external STORE/Write when VCC drops below it; VCAP supplies stored energy for STORE execution; and internal charge pump maintains VCAP at 5V. The device inhibits SRAM writes during low-voltage conditions and requires OE HIGH during writes to prevent bus contention.

Key Specifications

Pinout & Package

STK12C68-5K35M is packaged in a 28-pin CDIP (300 mil) with through-hole mounting and hermetic sealing for high-reliability applications. Pin assignments are identical across SMD5962-94599-compliant variants.

Key Features

Applications

Equivalent & Alternatives

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

Compared with STK12C68-5J55M, the -5K35M offers tighter timing for latency-critical control loops; versus FM24CL64-G, it delivers true autonomous power-loss STORE but requires capacitor management and has finite STORE endurance.

Availability

STK12C68-5K35M is available at Aetrix Electronics and suitable for avionics data logging, industrial PLC configuration memory, and telecom base station control memory requiring stable component supply, long-lifecycle support, and military-qualified reliability.

Supply support for STK12C68-5K35M 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, industrial, and automotive markets.

The STK12C68 series belongs to Cypress' nvSRAM product line, engineered specifically to replace battery-backed SRAM in mission-critical systems where maintenance-free, long-retention, and power-interruption-resilient memory is mandatory.

FAQ

What is the minimum VCAP capacitor value required for reliable AutoStore operation?

The STK12C68-5K35M requires a minimum 68 µF capacitor on VCAP, rated at 6V with ±20% tolerance. This value ensures sufficient energy to complete the 10 ms STORE cycle when VCC drops below VSWITCH (~3.6V). Using less capacitance risks incomplete STORE and data loss; values up to 220 µF are supported for extended hold-up time.

Can the HSB pin be left unconnected in systems that only use AutoStore or software STORE?

Yes-the HSB pin has an internal weak pull-up and may be left floating if hardware STORE is unused. However, leaving it unconnected forfeits STORE-in-progress status monitoring. For robust diagnostics, tie HSB to a GPIO with interrupt capability to detect and log STORE start/completion events during power transitions.

How does the STK12C68-5K35M handle simultaneous SRAM access and STORE initiation?

When HSB is pulled LOW or VCC crosses VSWITCH, the device completes any ongoing SRAM Read/Write within tDELAY (typically 100 ns), then inhibits new accesses. During STORE, all I/O pins are tri-stated and CE/WE/OE inputs are ignored until completion-ensuring atomic nonvolatile update without partial writes.

Is the software STORE sequence compatible with standard SRAM read timing, or does it require special timing margins?

The software STORE sequence uses standard CE-controlled Read cycles with no added timing constraints beyond datasheet tAA (35 ns) and tCE (35 ns). Each address must be latched cleanly; intervening writes or address glitches abort the sequence. No wait states or extended clocks are needed-compatibility with existing SRAM controllers is maintained.