Microchip Technology 25AA256-E/SM

Overview

25AA256-E/SM from Microchip Technology Inc. is a 256 Kbit SPI Serial EEPROM with 32,768 × 8-bit organization, 64-byte page size, and 1.8–5.5 V supply range. It supports up to 10 MHz clock frequency, offers hardware write protection via WP pin and STATUS register, and delivers 1 million erase/write cycles with >200-year data retention - deployed in industrial sensor nodes and automotive control modules for nonvolatile configuration storage.

For engineers reviewing the 25AA256-E/SM datasheet, 25AA256-E/SM pinout, 25AA256-E/SM application, or 25AA256-E/SM equivalent, key selection criteria include its extended temperature range (−40°C to +125°C), low standby current (1 µA), block-level write protection (0/¼/½/all array), HOLD functionality for interrupt-safe SPI pauses, and SOIC-8 (SM) packaging compatible with automated SMT assembly.

Technical Context

The 25AA256-E/SM implements a standard SPI Mode 0,0/Master-Slave interface with separate SI (data-in) and SO (data-out) lines, requiring CS, SCK, SI, SO, WP, HOLD, VCC, and VSS. Its internal architecture includes an 8-bit instruction register, page latches, HV generator, and EEPROM array with automatic address incrementing during sequential reads.

Write operations require explicit WREN instruction followed by CS high-to-low transition to initiate self-timed internal write cycle (≤5 ms). The STATUS register provides real-time WIP and WEL status, while BP0/BP1 bits enable configurable block protection - all nonvolatile and retained across power cycles.

Key Specifications

Pinout & Package

25AA256-E/SM is housed in an 8-lead SOIC package (JEDEC MS-012, body width 3.90 mm, "SM" suffix), with gull-wing leads, 1.27 mm pitch, and RoHS-compliant matte tin plating.

Key Features

Applications

Equivalent & Alternatives

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

Compared with 25AA256-E/SM, the 25LC256-I/SM sacrifices 1.8 V support for marginal cost reduction, while the AT25DF256A-SSH-T trades pin compatibility and endurance for quad-SPI speed - making 25AA256-E/SM optimal for extended-temperature, mixed-voltage, and safety-critical deployments.

Availability

25AA256-E/SM is available at Aetrix Electronics and suitable for industrial sensor nodes, automotive engine control units, and medical infusion pumps requiring stable component supply across extended temperature ranges and long product lifecycles.

Supply support for 25AA256-E/SM 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

Microchip Technology Inc. is a leading provider of microcontrollers, analog, FPGA, and memory solutions, serving automotive, industrial, consumer, and communications markets with vertically integrated silicon and development tools.

The 25AA256-E/SM belongs to Microchip's serial EEPROM product line, designed specifically for robust, low-power, SPI-based nonvolatile storage in harsh environments - emphasizing reliability, wide voltage operation, and automotive-grade qualification.

FAQ

What is the operating voltage range for the 25AA256-E/SM?

The 25AA256-E/SM operates from 1.8 V to 5.5 V, supporting both low-voltage logic families (e.g., 1.8 V MCUs) and legacy 5 V systems. This wide range eliminates level-shifting requirements in mixed-voltage designs and ensures compatibility with battery-powered applications down to single-cell Li-ion or alkaline configurations. The 25AA256-E/SM maintains full functionality-including 10 MHz max clock and 1 µA standby current-across the entire range.

Does the 25AA256-E/SM support hardware write protection?

Yes, the 25AA256-E/SM supports dual-layer hardware write protection: the WP pin (Pin 3) combined with the WPEN bit in the STATUS register enables selective locking of the STATUS register itself. When WP is low and WPEN = 1, writes to nonvolatile STATUS bits are blocked - preventing accidental changes to block protection settings. Memory array writes remain unaffected unless BP0/BP1 bits are set to protect specific regions. This design allows safe field updates while preserving critical configuration integrity.

How does the HOLD function work on the 25AA256-E/SM?

The HOLD pin (Pin 7) suspends ongoing SPI communication without resetting the internal state - allowing the host MCU to service time-critical interrupts and resume exactly where it left off. To activate HOLD, the pin must be pulled low while SCK is low; releasing HOLD while SCK remains low resumes transmission. During HOLD, SI, SCK, and SO enter high-impedance, and only CS retains control. This behavior is essential for deterministic real-time systems where SPI transactions cannot be aborted or restarted.

What is the maximum write speed and page size of the 25AA256-E/SM?

The 25AA256-E/SM supports up to 10 MHz SPI clock (at VCC ≥ 4.5 V), enabling byte writes in ~1.6 µs and page writes (64 bytes) in ≤5 ms. Its fixed 64-byte page size defines the largest atomic write unit - attempting to write across a page boundary causes wraparound within the current page. This constraint requires firmware to align multi-byte writes to page boundaries or implement split-page logic, ensuring data integrity during power loss.

Is the 25AA256-E/SM qualified for automotive applications?

Yes, the 25AA256-E/SM is AEC-Q100 qualified for Extended Temperature Grade (−40°C to +125°C), meeting rigorous automotive reliability standards for humidity, thermal cycling, and vibration. It is explicitly rated for under-hood use in engine control, transmission, and ADAS modules. The qualification includes 1 million endurance cycles and >200-year data retention at 125°C - exceeding typical automotive lifecycle requirements and eliminating need for external qualification testing.