Infineon Technologies STK12C68-C45

Overview

STK12C68-C45 from Cypress Semiconductor is a 64 Kbit (8K × 8) nonvolatile static RAM with QuantumTrap technology, operating at 5 V ±10%, delivering 45 ns access time, auto-initiated STORE on power loss using an external 68 µF capacitor, and supporting software/hardware-controlled STORE/RECALL. It serves as a drop-in SRAM replacement in mission-critical industrial controllers where data persistence across power cycles is mandatory.

For engineers reviewing the STK12C68-C45 datasheet, STK12C68-C45 pinout, STK12C68-C45 application, or STK12C68-C45 equivalent, key selection criteria include AutoStore timing dependency on VCAP capacitance, HSB-driven hardware STORE arbitration, software STORE address sequence integrity, and 1 million STORE endurance versus unlimited RECALL cycles.

Technical Context

The STK12C68-C45 integrates parallel SRAM and QuantumTrap nonvolatile cells per bit, enabling simultaneous STORE/RECALL of all 8,192 bytes. Its AutoStore operation triggers when VCC drops below VSWITCH (~3.6 V), using charge stored on the external VCAP capacitor to complete a single 10 ms STORE cycle without host intervention.

STORE is conditional: hardware or AutoStore only executes if at least one SRAM write occurred since the last STORE or RECALL. Software STORE bypasses this condition and uses a six-address CE-controlled read sequence (0x0000 → 0x0F0F); software RECALL uses identical sequence ending in 0x0F0E. HSB pin functions as both input (to request STORE) and open-drain output (to signal busy).

Key Specifications

Pinout & Package

STK12C68-C45 is packaged in a 28-pin 300-mil PDIP (Plastic Dual In-line Package), pin-compatible with industry-standard 28-pin SRAM footprints. Pin spacing is 0.1 inch (2.54 mm), with 0.3 inch body width.

Key Features

Applications

Equivalent & Alternatives

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

Compared with STK12C68-C35, the -C45 variant trades 10 ns slower access for broader voltage margin tolerance in noisy industrial rails; versus AS6C8008-55ZIN, it eliminates backup power design complexity but adds VCAP layout constraints and STORE timing validation overhead.

Availability

STK12C68-C45 is available at Aetrix Electronics and suitable for industrial PLCs, medical diagnostic equipment, and avionics black box recorders requiring stable component supply with guaranteed long-term manufacturability.

Supply support for STK12C68-C45 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 industrial, automotive, and communications infrastructure.

The STK12C68 belongs to Cypress' QuantumTrap nvSRAM product line, engineered specifically for systems needing SRAM-speed performance with EEPROM-like nonvolatility-eliminating batteries, supercaps, and complex backup power sequencing.

FAQ

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

The STK12C68-C45 requires a minimum of 68 µF (±20%) tantalum or low-ESR electrolytic capacitor on VCAP to guarantee full 10 ms STORE completion during power loss. Capacitance below this value risks partial STORE failure and data corruption; values up to 220 µF extend hold time margin but increase board area and inrush current at power-on.

Can STK12C68-C45 be used without connecting the VCAP pin?

No. VCAP must be connected to a compliant capacitor for AutoStore functionality. If nonvolatile storage is not needed, the device can operate in SRAM-only mode only if configured in AutoStore Inhibit mode (VCAP = +5 V, VCC = GND), but this disables automatic power-loss STORE and requires software or HSB initiation for every STORE-defeating the core value proposition.

How does the conditional STORE feature affect firmware design?

The STK12C68-C45 skips AutoStore and HSB-triggered STORE unless at least one SRAM write occurred since the last STORE or RECALL. Firmware must ensure a dummy write (e.g., to a reserved flag location) precedes critical updates if deterministic STORE timing is required-software STORE sequences are exempt from this condition and always execute.

Is STK12C68-C45 RoHS compliant and lead-free?

Yes. The STK12C68-C45 is RoHS compliant and manufactured with lead-free terminations per JEDEC J-STD-609. The 28-pin PDIP package uses matte tin plating, and the device meets IPC/JEDEC J-STD-020 moisture sensitivity level MSL-3, requiring bake conditioning only if exposed to ambient >60% RH for >168 hours before reflow.