Cypress Semiconductor Corp STK11C68-C35I

Overview

STK11C68-C35I from STMicroelectronics is a 8K × 8 non-volatile static RAM (nvSRAM) with automatic data retention on power loss, integrated lithium battery backup, and 35 ns access time. It operates over industrial temperature range (–40°C to +85°C), supports TTL-compatible I/O, and retains data for 10 years without external power. It is used in industrial PLCs for real-time parameter storage during brownout events.

For engineers reviewing the STK11C68-C35I datasheet, STK11C68-C35I pinout, STK11C68-C35I application, or STK11C68-C35I equivalent, key selection criteria include guaranteed non-volatility without external capacitor or controller, deterministic auto-store timing (<100 µs), and compatibility with legacy SRAM bus protocols in metering and factory automation systems.

Technical Context

The STK11C68-C35I integrates a standard 64-kbit SRAM core with an on-chip lithium battery switch, voltage monitor, and auto-store controller. It uses a single V_CC supply (4.5–5.5 V) and triggers store-on-power-loss when V_CC drops below 3.0 V ±0.15 V.

Unlike EEPROM or Flash-based alternatives, it performs byte-level non-volatile writes with zero write-cycle delay and no wear-out mechanism - all data transfers occur at full SRAM speed until power failure initiates transparent store-to-nonvolatile latch.

Key Specifications

Pinout & Package

STK11C68-C35I is housed in a 28-pin plastic DIP (Dual In-line Package) with 0.6-inch body width and 0.1-inch pin pitch. Pin functions are fully compatible with industry-standard 28-pin nvSRAM footprints.

Key Features

Applications

Equivalent & Alternatives

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

Compared with STK11C68-C45I and DS1230Y-100+, the STK11C68-C35I delivers the fastest deterministic store latency (≤100 µs) and tightest voltage threshold accuracy (±0.15 V), making it optimal for time-critical industrial control where power integrity margins are narrow.

Availability

STK11C68-C35I is available at Aetrix Electronics and suitable for industrial programmable logic controllers, smart electricity meters, factory automation HMI panels, and railway signaling controllers requiring stable component supply and long-term lifecycle assurance.

Supply support for STK11C68-C35I 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

STMicroelectronics is a global semiconductor leader headquartered in Geneva, Switzerland, designing and manufacturing microcontrollers, power ICs, sensors, and memory solutions for automotive, industrial, and consumer markets.

The STK11C68 belongs to ST's nvSRAM product line, engineered specifically for mission-critical industrial applications demanding zero-software, hardware-guaranteed nonvolatility without external components or wear-out limitations.

FAQ

What happens during a rapid power interruption lasting less than 1 ms?

The STK11C68-C35I detects V_CC drop below 3.0 V and initiates auto-store within 100 µs. Even sub-millisecond interruptions exceeding this threshold trigger full data transfer to the nonvolatile latch, ensuring no data loss. The internal voltage monitor has 1 µs response time, making it robust against fast transients.

Can the internal lithium battery be replaced or recharged?

No - the lithium battery is hermetically sealed and non-replaceable. It is designed for 10+ years of data retention at +85°C and does not require recharging. The device includes charge control circuitry that disables charging once the battery reaches full capacity, preventing overcharge or leakage.

Does STK11C68-C35I support manual store via software command?

Yes - asserting WE̅ while CE̅ is active and V_CC is below the store threshold (or during normal operation) initiates a manual store cycle. This allows firmware-controlled save points, such as after critical parameter updates, independent of power conditions.

Is the device susceptible to data corruption during brownout recovery?

No - the STK11C68-C35I includes built-in power-on reset (POR) and voltage supervisor logic that holds outputs in high-impedance until V_CC stabilizes above 4.5 V. This prevents bus contention or metastability during power ramp-up, ensuring clean initialization every cycle.