Infineon Technologies STK12C68-PF45

Overview

STK12C68-PF45 from Cypress Semiconductor is a 64 Kbit (8 K × 8) nonvolatile static RAM with QuantumTrap technology, operating at 5 V ±10% and featuring 45 ns access time. It integrates SRAM and nonvolatile storage in each cell, enabling automatic STORE on power-down using an external 68 µF capacitor and software/hardware-controlled STORE/RECALL. Used in industrial control systems requiring persistent memory without battery backup.

For engineers reviewing the STK12C68-PF45 datasheet, STK12C68-PF45 pinout, STK12C68-PF45 application, or STK12C68-PF45 equivalent, key selection criteria include AutoStore timing, VCAP capacitor requirements, HSB pin behavior, SRAM compatibility, and 1 million STORE endurance - all critical for fail-safe data retention in unattended equipment.

Technical Context

The STK12C68-PF45 implements a dual-cell architecture: standard fast SRAM (25–45 ns access) paired with parallel QuantumTrap nonvolatile elements. STORE and RECALL operate atomically across all 8,192 bytes, with hardware STORE triggered via HSB pin and software STORE initiated by a six-address CE-controlled read sequence (0x0000 → 0x0F0F).

AutoStore activates when VCC drops below VSWITCH (~3.6 V), using charge stored on the external VCAP capacitor to complete a single 10 ms STORE cycle. During STORE/RECALL, SRAM reads/writes are inhibited, and HSB asserts low to signal busy status - a critical timing constraint for system-level power sequencing and firmware coordination.

Key Specifications

Pinout & Package

STK12C68-PF45 is supplied in a 28-pin Plastic Dual In-line Package (PDIP) with 300 mil body width, RoHS-compliant lead finish, and through-hole mounting.

Key Features

Applications

Equivalent & Alternatives

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

Compared with STK12C68-CF45, the PF45 variant adds industrial temperature support and tighter VCC tolerance - essential for outdoor or factory-floor use. Versus FM24CL64-G, the STK12C68-PF45 delivers full parallel bus performance and deterministic STORE timing, but demands careful VCAP layout and power-rail monitoring.

Availability

STK12C68-PF45 is available at Aetrix Electronics and suitable for industrial PLC data logging, medical device configuration storage, and telecom base station control memory requiring stable component supply and long-term lifecycle assurance.

Supply support for STK12C68-PF45 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 markets.

The STK12C68 product line was designed to replace battery-backed SRAM in mission-critical systems where maintenance-free, high-reliability nonvolatility is required - particularly in environments with thermal stress, vibration, or regulatory restrictions on batteries.

FAQ

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

The STK12C68-PF45 requires a minimum 68 µF ±20% tantalum or low-ESR electrolytic capacitor rated for 6 V. Values below this threshold risk incomplete STORE execution during rapid VCC collapse, especially at high temperature or after multiple STORE cycles due to capacitor aging. The internal charge pump maintains VCAP at ~5 V during normal operation, so capacitor ESR must remain below 1 Ω to sustain 10 ms STORE current.

Can STK12C68-PF45 be used with a 3.3 V system?

No - STK12C68-PF45 is specified exclusively for 5 V ±10% operation (4.5 V to 5.5 V). Its internal charge pump, VSWITCH threshold (~3.6 V), and QuantumTrap programming voltage require 5 V rails. Interfacing with 3.3 V logic necessitates level-shifting on all address, data, and control lines, and VCC must still be supplied at 5 V. There is no 3.3 V variant in the STK12C68 family.

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

The HSB pin goes LOW during software-initiated STORE, exactly as during AutoStore or hardware STORE. This provides consistent busy signaling regardless of initiation method. The pin remains LOW for the full tSTORE duration (max 10 ms), then releases open-drain HIGH. Systems must monitor HSB or implement timeout-based polling, since no interrupt is generated - critical for firmware that must pause memory access during persistence operations.

Is STK12C68-PF45 recommended for new designs?

No - Cypress explicitly marks STK12C68 as "Not Recommended for New Designs" in its official documentation (Rev. *H, Nov 2014). While fully functional and supported for existing production, Infineon recommends migrating to newer nvSRAM families like the CY14B108 or F-RAM alternatives for new projects due to enhanced density, lower power, and extended lifecycle support.