Cypress Semiconductor Corp STK12C68-5K55M

Overview

STK12C68-5K55M from Cypress Semiconductor is a 64 Kbit (8K × 8) nonvolatile static RAM with QuantumTrap™ technology, delivering 55 ns access time, AutoStore™ on power-down, and software/hardware-controlled STORE/RECALL operations. It operates at single 5V ±10%, supports military temperature range (−55°C to +125°C), and uses a 28-pin LCC package for embedded systems requiring persistent SRAM state without battery backup.

For engineers reviewing the STK12C68-5K55M datasheet, STK12C68-5K55M pinout, STK12C68-5K55M application, or STK12C68-5K55M equivalent, key selection criteria include VCAP capacitor sizing (68 µF), HSB-driven hardware store timing (tDELAY), STORE cycle endurance (1 million cycles), and software address sequence integrity (0x0000 → 0x0F0F for STORE).

Technical Context

The STK12C68-5K55M integrates parallel SRAM and QuantumTrap nonvolatile cells per bit, enabling simultaneous STORE/RECALL across all 8,192 bytes. Its architecture decouples volatile read/write (unlimited cycles) from nonvolatile storage (1M STOREs, 100-year retention), with automatic power-loss detection via VSWITCH threshold (~3.6V) and internal charge pump driving VCAP to 5V.

STORE is initiated by three independent methods: AutoStore on VCC drop below VSWITCH, hardware trigger via HSB pin (open-drain busy indicator), or six-step CE-controlled read sequence (0x0000, 0x1555, 0x0AAA, 0x1FFF, 0x10F0, 0x0F0F). RECALL occurs automatically on power-up or via software sequence ending at 0x0F0E, with tHRECALL ≤ 20 ms and full SRAM restoration without NV data loss.

Key Specifications

Pinout & Package

Package: 28-pad Leadless Chip Carrier (LCC), 300-mil body, surface-mountable with J-lead profile per MIL-STD-883.

Key Features

Applications

Equivalent & Alternatives

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

Compared with CY14B108L-BA25XI and FM1808-55-TG, the STK12C68-5K55M uniquely supports 5V parallel bus operation, military temperature range, HSB-driven hardware STORE, and software-initiated STORE/RECALL - making it irreplaceable in legacy avionics and ruggedized metering where backward compatibility and deterministic power-loss response are mandatory.

Availability

STK12C68-5K55M is available at Aetrix Electronics and suitable for smart energy meters, avionics flight recorders, and industrial PLC I/O modules requiring stable component supply across extended product lifecycles.

Supply support for STK12C68-5K55M 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 programmable solutions for industrial, automotive, and aerospace markets.

The STK12C68-5K55M belongs to Cypress's nvSRAM product line, engineered specifically for mission-critical systems where data persistence must survive instantaneous power loss without batteries or complex supervision circuitry.

FAQ

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

The STK12C68-5K55M requires a minimum 68 µF tantalum or polymer capacitor rated at 6V ±20% on the VCAP pin. This value ensures sufficient stored energy to complete the 10 ms STORE cycle when VCC drops below VSWITCH (~3.6V). Using less capacitance risks incomplete STORE and data loss; values up to 220 µF are supported for extended hold-up time.

Can the STK12C68-5K55M be operated without connecting the VCAP pin?

No - VCAP must be connected to a properly sized capacitor for AutoStore functionality. If VCAP is left floating or shorted, the device cannot perform power-loss STORE operations. In AutoStore Inhibit mode (VCC grounded, +5V applied to VCAP), VCAP remains connected but serves as primary supply; however, this disables automatic power-down STORE and requires explicit software or HSB triggering.

How does the STK12C68-5K55M prevent unintended STORE during power-up?

The device inhibits STORE initiation until at least one valid SRAM write occurs after the most recent RECALL or STORE cycle. During power-up, internal logic monitors VCC against VSWITCH and blocks HSB- or AutoStore-triggered STORE unless a write has been performed - preventing spurious STOREs caused by noise or partial initialization. The 10 kΩ pull-up on WE or CE further prevents accidental writes.

Is the software STORE sequence compatible with all bus timing configurations?

Yes - the six-address software STORE sequence (0x0000 → 0x0F0F) relies solely on CE-controlled read cycles and is timing-agnostic. As long as each read completes before the next address is presented, and no intervening writes occur, the sequence functions across varying bus speeds. OE may be HIGH or LOW during the sequence; only CE transitions matter for clocking the address steps.