Microchip Technology 25AA256T-E/SM

Overview

25AA256T-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, delivers ≤5 mA write current at 5.5 V, and provides hardware write protection via WP pin and STATUS register. It is used in industrial and automotive systems for firmware parameter storage, calibration data retention, and configuration backup.

For engineers reviewing the 25AA256T-E/SM datasheet, 25AA256T-E/SM pinout, 25AA256T-E/SM application, or 25AA256T-E/SM equivalent, key selection criteria include its extended temperature range (–40°C to +125°C), AEC-Q100 qualification, low 1 µA standby current, and block-level write protection enabling selective array locking in safety-critical embedded designs.

Technical Context

The 25AA256T-E/SM implements a standard SPI Mode 0,0/M1,1 interface with separate SI and SO 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 rollover during sequential reads.

It features dual-layer write protection: volatile WREN/WRDI-controlled latch and nonvolatile BP0/BP1 bits in the STATUS register, plus hardware-enforced protection when WP is low and WPEN is high. All writes require explicit WREN activation and CS high-to-low transition to initiate internal 5 ms max. self-timed erase/write cycles.

Key Specifications

Pinout & Package

25AA256T-E/SM is housed in an 8-lead SOIC package (SN designation), 3.90 mm body width, RoHS-compliant matte tin finish. Pin 1 is marked with a beveled corner or dot; orientation follows JEDEC MS-012 standard.

Key Features

Applications

Equivalent & Alternatives

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

Compared with 25AA256T-E/SM, the 25LC256-I/SN offers identical packaging and footprint but sacrifices 1.8 V operation and automotive qualification, while the AT25DF256A-SSH-T trades pin compatibility and HOLD functionality for faster quad-SPI access - making 25AA256T-E/SM optimal for drop-in replacement in legacy 1.8–5.5 V AEC-Q100 designs requiring deterministic interrupt latency.

Availability

25AA256T-E/SM is available at Aetrix Electronics and suitable for industrial PLC configuration storage, automotive ECU calibration logging, medical infusion pump calibration, and smart energy meter firmware backup requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for 25AA256T-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 microcontroller, analog, FPGA, and memory solutions, headquartered in Chandler, Arizona, with global design and manufacturing operations.

The 25AA256T-E/SM belongs to Microchip's serial EEPROM product line, engineered for robust, low-power nonvolatile data storage in automotive, industrial, and medical applications demanding AEC-Q100 qualification and extended temperature operation.

FAQ

What is the maximum clock frequency supported by the 25AA256T-E/SM?

The 25AA256T-E/SM supports up to 10 MHz clock frequency when VCC is 4.5–5.5 V, 5 MHz at 2.5–4.5 V, and 3 MHz at 1.8–2.5 V. These limits ensure reliable setup/hold timing for SI and SO signals across its full operating voltage and temperature range. The 25AA256T-E/SM datasheet specifies AC characteristics including TCSS, THD, and TV to validate timing margins at each voltage tier.

Does the 25AA256T-E/SM support hardware write protection?

Yes, the 25AA256T-E/SM supports hardware write protection via the WP pin in conjunction with the WPEN bit in the STATUS register. When WP is low and WPEN = 1, writes to nonvolatile STATUS bits (BP0, BP1, WPEN) are blocked - protecting critical protection settings from accidental overwrite. The 25AA256T-E/SM retains this behavior across power cycles and temperature extremes.

What is the page size and maximum write length for the 25AA256T-E/SM?

The 25AA256T-E/SM has a fixed 64-byte page size. Up to 64 bytes can be written in a single page write operation, provided all addresses fall within the same physical page boundary (e.g., 0x0000–0x003F). Crossing a page boundary causes wraparound within the current page - a behavior explicitly documented in the 25AA256T-E/SM functional description to prevent silent data corruption.

Is the 25AA256T-E/SM qualified for automotive applications?

Yes, the 25AA256T-E/SM is AEC-Q100 qualified for Grade 1 (–40°C to +125°C) operation. This qualification includes stress testing for temperature cycling, high-temperature operating life (HTOL), and electrostatic discharge (>4 kV HBM), confirming suitability for engine control, transmission, and body electronics applications. The "E" suffix in 25AA256T-E/SM denotes extended temperature grade compliance.

How does the HOLD function operate on the 25AA256T-E/SM?

The HOLD pin on the 25AA256T-E/SM suspends ongoing SPI communication when pulled low while SCK is low, placing SO, SI, and SCK in high-impedance states. Communication resumes from the exact point of suspension when HOLD is returned high with SCK low - eliminating retransmission overhead. This behavior is electrically characterized in the 25AA256T-E/SM AC timing table (THS, THH, THV, THZ).