Infineon Technologies STK12C68-L35I

Overview

STK12C68-L35I from Cypress Semiconductor is a 64 Kbit (8K × 8) nonvolatile SRAM with QuantumTrap technology, delivering 35 ns access time, AutoStore on power loss using a 68 µF VCAP capacitor, and unlimited SRAM read/write cycles. It operates at single 5V ±10%, supports software/hardware STORE/RECALL, and is used in industrial control systems requiring persistent memory without battery backup.

For engineers reviewing the STK12C68-L35I datasheet, STK12C68-L35I pinout, STK12C68-L35I application, or STK12C68-L35I equivalent, key selection considerations include AutoStore timing constraints (tSTORE = 10 ms), HSB-controlled hardware store arbitration, VCAP charge retention behavior, and compatibility with legacy 28-pin DIP/SOIC footprints in mission-critical data logging and PLC modules.

Technical Context

The STK12C68-L35I 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 functions as standard fast memory while QuantumTrap provides 100-year data retention and 1M STORE endurance.

STORE is triggered by power-down voltage drop below VSWITCH (~3.6 V), HSB assertion, or six-address software sequence; RECALL occurs automatically at power-up or via identical six-address sequence ending in 0x0F0E. During STORE/RECALL, SRAM I/O is disabled and HSB asserts low to signal busy state.

Key Specifications

Pinout & Package

STK12C68-L35I uses a 28-pin plastic dual in-line package (PDIP), 600 mil width, with through-hole mounting. Pin assignments match industry-standard 28-pin SRAM footprints for drop-in compatibility.

Key Features

Applications

Equivalent & Alternatives

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

Compared with CY14B108L-ZSP25XI and FM24CL64-G, STK12C68-L35I uniquely delivers parallel-byte access, deterministic 10 ms STORE timing, and legacy 28-pin DIP compatibility-making it irreplaceable in field-deployed industrial hardware where board-level redesign is prohibited.

Availability

STK12C68-L35I is available at Aetrix Electronics and suitable for industrial PLCs, medical diagnostics equipment, avionics black boxes, and smart energy meters requiring stable component supply and long-term obsolescence support.

Supply support for STK12C68-L35I 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 U.S.-based semiconductor company specializing in memory, microcontrollers, and connectivity solutions for industrial, automotive, and consumer applications.

The STK12C68 product line was designed specifically for legacy system upgrades requiring battery-free nonvolatility in standard SRAM footprints-targeting industrial control, instrumentation, and telecom infrastructure.

FAQ

What is the minimum VCC voltage required to complete an AutoStore operation?

The STK12C68-L35I requires VCC to remain ≥3.6 V for the full 10 ms STORE duration. If VCC drops below this threshold before completion, the STORE aborts and data may be lost. System design must ensure sufficient hold-up time from bulk capacitance or VCAP sizing to meet this requirement under worst-case load conditions.

Can the HSB pin be left unconnected in a design that uses only 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 real-time STORE progress monitoring. For robustness in safety-critical systems, tie HSB to a GPIO with interrupt capability to detect and log STORE completion or timeout events.

Does the STK12C68-L35I require external circuitry to prevent spurious STORE during power-up?

Yes-a 10 kΩ pull-up resistor on WE (to VCC) is mandatory to hold WE HIGH at power-up and prevent accidental writes during voltage ramp. This is specified in the datasheet to avoid SRAM corruption before firmware initializes control signals, especially in systems lacking reset supervision.

How does the STK12C68-L35I handle concurrent SRAM access and STORE initiation?

When HSB is asserted or VCC drops, the device completes any active SRAM read/write within tDELAY (typically 100 ns), then disables I/O and begins STORE. Ongoing writes finish before STORE starts; new writes are inhibited until HSB returns HIGH. This ensures data coherency without external arbitration logic.