Cypress Semiconductor Corp STK12C68-L45I

Overview

STK12C68-L45I from Cypress Semiconductor is a 64 Kbit (8K × 8) nonvolatile static RAM with QuantumTrap technology, delivering 45 ns access time, single 5V ±10% operation, and hands-off AutoStore on power loss using an external 68 µF capacitor. It performs STORE/RECALL between SRAM and nonvolatile elements, supporting industrial temperature range (–40°C to +85°C) in a 28-pin SOIC package for embedded control and data logging systems.

For engineers reviewing the STK12C68-L45I datasheet, STK12C68-L45I pinout, STK12C68-L45I application, or STK12C68-L45I equivalent, key selection criteria include AutoStore timing behavior, HSB-controlled hardware store latency, VCAP capacitor sizing requirements, and software STORE/RECALL address sequence compliance.

Technical Context

The STK12C68-L45I integrates parallel SRAM (128 × 512) and QuantumTrap nonvolatile memory (128 × 512) in each cell, enabling simultaneous STORE/RECALL of all 8,192 bytes. It supports three STORE triggers: AutoStore on VCC drop below VSWITCH (~3.6 V), hardware STORE via HSB pin assertion, and software STORE via six-address CE-controlled read sequence (0x0000 → 0x0F0F).

RECALL occurs automatically at power-up when VCC exceeds VSWITCH (tHRECALL = 10 ms max), or via software sequence ending at 0x0F0E. During STORE/RECALL, SRAM reads/writes are inhibited, and HSB asserts open-drain LOW to signal busy state - critical for system-level power sequencing coordination.

Key Specifications

Pinout & Package

STK12C68-L45I is housed in a 28-pin Small Outline Integrated Circuit (SOIC) package, 300 mil width, RoHS-compliant, with 1.27 mm pitch and surface-mount footprint.

Key Features

Applications

Equivalent & Alternatives

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

Compared with CY14B108L-ZSP25XI and FM24CL64B-G, STK12C68-L45I provides direct SRAM drop-in replacement capability, deterministic AutoStore without host intervention, and guaranteed 45 ns timing - essential for legacy parallel-bus industrial controllers maintaining long-lifecycle BOMs.

Availability

STK12C68-L45I is available at Aetrix Electronics and suitable for industrial PLC data logging, motor drive parameter storage, and telecom line card configuration requiring stable component supply and long-term lifecycle support.

Supply support for STK12C68-L45I 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 logic solutions for industrial, automotive, and communications markets.

The STK12C68 product line delivers nonvolatile SRAM with QuantumTrap technology, targeting applications needing instant-on recall, unlimited write endurance, and autonomous power-loss data preservation without batteries or external controllers.

FAQ

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

The STK12C68-L45I requires a minimum 68 µF ±20% tantalum or low-ESR electrolytic capacitor rated for 6 V on the VCAP pin. This ensures sufficient stored energy to complete the 10 ms STORE cycle when VCC drops below VSWITCH (3.6 V). Using less capacitance risks incomplete STORE and data loss; values up to 220 µF are supported for extended hold-up time.

Can STK12C68-L45I be used in place of a standard 8K × 8 SRAM without design changes?

Yes - STK12C68-L45I is pin-compatible with industry-standard 28-pin SOIC SRAMs (e.g., IS61LV256AL), sharing identical address/data/control pinouts and timing. However, VCAP must be populated with a 68 µF capacitor, and WE must be pulled HIGH at power-up to prevent spurious writes during RECALL. No firmware changes are needed for basic SRAM operation.

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

The HSB pin asserts LOW during *any* STORE or RECALL operation - including those initiated by software address sequence - and remains LOW for the full tSTORE duration (≤10 ms). This allows the host system to monitor HSB to synchronize peripheral activity, disable interrupts, or gate clocks during nonvolatile transfer, ensuring deterministic timing regardless of initiation method.

Is STK12C68-L45I suitable for new designs, or is it obsolete?

STK12C68-L45I is Not Recommended for New Designs per Cypress documentation (Rev. *C, March 2011), but remains in production solely to support ongoing manufacturing programs. Aetrix Electronics maintains active inventory and supply chain continuity for legacy industrial and medical equipment requiring exact form-fit-function replacement with documented lifecycle management.