Simtek STK17T88-RF25

Overview

STK17T88-RF25 from Cypress Semiconductor is a 32K × 8 (256 Kb) nonvolatile SRAM with integrated real-time clock, watchdog timer, alarm, and power monitor. It operates from a single 3.0V ±10% supply, delivers 25 ns read access time, supports automatic STORE on power loss and RECALL on power-up, and uses a 48-pin SSOP package for industrial temperature range (–40°C to +85°C).

For engineers reviewing the STK17T88-RF25 datasheet, STK17T88-RF25 pinout, STK17T88-RF25 application, or STK17T88-RF25 equivalent, key selection criteria include nvSRAM endurance (unlimited reads/writes), RTC accuracy with leap-year support, hardware/software-controlled STORE/RECALL, VCAP-backed data retention, and interrupt-driven alarm/watchdog functionality.

Technical Context

The STK17T88-RF25 integrates a QuantumTrap-based nvSRAM array (512 × 512) with a fully autonomous RTC subsystem featuring programmable oscillator calibration, minute/hour/day alarm modes, and a reset-capable watchdog timer. Its power management includes dual backup paths-capacitive (VRCTcap) or battery (VRTCbat)-and a dedicated VCAP pin enabling automatic STORE during brownout.

Memory operation supports three STORE modes: AutoStore (hardware-triggered on VCC drop), HSB-initiated hardware STORE, and software-commanded STORE via register writes; RECALL occurs automatically at power-up or via software command. The RTC register map (16 bytes) is accessed through the same DQ0–DQ7 bus using address A14–A0, with INT pin configurable as push-pull or open-drain output.

Key Specifications

Pinout & Package

Package: 48-pin 300-mil SSOP (RoHS compliant), footprint-compatible with industry-standard 48-SSOP layouts.

Key Features

Applications

Equivalent & Alternatives

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

Compared with STK17TA8-RF25, the STK17T88-RF25 trades extended temperature rating for lower cost and identical performance in commercial/industrial settings; versus DS1248W-120+T&R, it offers 5× faster access, integrated crystal drive, and smaller 48-SSOP footprint-making it superior for new designs requiring speed, integration, and compactness.

Availability

STK17T88-RF25 is available at Aetrix Electronics and suitable for smart energy metering, industrial PLC controllers, medical diagnostic equipment, and automotive telematics units requiring stable component supply and long-term data integrity.

Supply support for STK17T88-RF25 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 mixed-signal solutions for embedded systems.

The STK17T88 belongs to Cypress's AutoStore nvSRAM product line, designed to eliminate external nonvolatile memory and discrete RTC components in mission-critical applications where data persistence and timekeeping must survive power interruption.

FAQ

What is the role of the VCAP pin, and what capacitor value is required?

The VCAP pin supplies hold-up energy to complete the STORE operation during VCC dropout. A 17–57 µF tantalum or polymer capacitor rated for ≥5 V must be connected between VCAP and VSS. Typical value is 47 µF; values outside this range risk incomplete STORE or excessive inrush current.

Can the STK17T88-RF25 operate without an external crystal?

No-the X1 and X2 pins require a 32.768 kHz crystal for RTC operation. The internal oscillator drives X1 and receives feedback from X2; omitting the crystal disables all RTC functions (clock, alarm, watchdog), though nvSRAM remains fully functional.

How does the HSB pin function in both input and output modes?

HSB is an open-drain bidirectional pin: when unconnected, its internal weak pull-up holds it high; pulling it low externally initiates a hardware STORE. During STORE, it outputs low to signal busy status. This dual role eliminates need for separate control and status lines.

Is the STK17T88-RF25 still recommended for new designs?

No-Cypress documentation explicitly marks STK17T88 as "Not Recommended for New Designs." It remains available for legacy support, but Infineon recommends migrating to newer nvSRAM+RTC families such as the CY14X series for enhanced reliability, longer retention, and extended temperature support.