Microchip Technology 25AA256-E/MF

Overview

25AA256-E/MF from Microchip Technology Inc. is a 256 Kbit (32,768 × 8) SPI serial EEPROM with 1.8–5.5 V supply range, 64-byte page write capability, and automotive-grade AEC-Q100 qualification for extended temperature operation (−40°C to +125°C). It features hardware write protection via WP pin and STATUS register, HOLD functionality for interrupt-safe bus suspension, and self-timed 5 ms max write cycles - deployed in engine control units, battery management systems, and industrial sensor calibration storage.

For engineers reviewing the 25AA256-E/MF datasheet, 25AA256-E/MF pinout, 25AA256-E/MF application, or 25AA256-E/MF equivalent, key selection criteria include its 1.8 V minimum VCC support, AEC-Q100 Grade 1 qualification, 8-lead DFN (MF) package footprint, and SPI Mode 0,0/1,1 compatibility with PIC® and ARM-based microcontrollers.

Technical Context

The 25AA256-E/MF implements a standard SPI interface with separate SI (MOSI) and SO (MISO) lines, requiring CS, SCK, and optional HOLD/WP signals. Its internal architecture includes a 64-byte page latch, nonvolatile STATUS register with BP0/BP1 block protection bits, and HV generator for EEPROM programming - all managed by dedicated memory control logic.

Write operations require explicit WREN instruction followed by CS high-to-low transition to initiate TWC (5 ms max); read operations support sequential addressing with automatic address rollover at 7FFFh. The HOLD pin suspends ongoing transfers without resetting the internal state, enabling deterministic interrupt handling in real-time embedded systems.

Key Specifications

Pinout & Package

25AA256-E/MF uses an 8-lead DFN (Dual Flat No-lead) package, 3 mm × 2 mm body, 0.5 mm pitch, exposed thermal pad (non-electrical), JEDEC MO-229 compliant. Pin 1 marked by beveled corner; pins are unidirectional and not internally multiplexed.

Key Features

Applications

Equivalent & Alternatives

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

Compared with 25LC256-I/MF and AT25DF256A-MHN-T, the 25AA256-E/MF uniquely combines 1.8 V operation, AEC-Q100 Grade 1 qualification, and HOLD functionality - making it the only option for automotive-grade, low-voltage, interrupt-resilient EEPROM applications.

Availability

25AA256-E/MF is available at Aetrix Electronics and suitable for automotive ECU development, battery management systems, and industrial sensor calibration requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for 25AA256-E/MF 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 25AA256 is part of Microchip's serial EEPROM product line designed specifically for automotive, industrial, and medical applications demanding high reliability, extended temperature operation, and robust data integrity features.

FAQ

What is the minimum supply voltage required for reliable operation of the 25AA256-E/MF?

The 25AA256-E/MF operates reliably from 1.8 V to 5.5 V. At 1.8 V, maximum clock frequency is 3 MHz per AC characteristics Table 1-2, and all features-including page write, HOLD, and WP protection-remain fully functional. This makes the 25AA256-E/MF suitable for battery-powered and energy-harvesting systems where supply voltage may fall below 2.5 V. The 25AA256-E/MF does not require external level shifters when interfaced with 1.8 V MCUs.

Does the 25AA256-E/MF support SPI Mode 0,0 and Mode 1,1 simultaneously?

Yes, the 25AA256-E/MF supports both SPI Mode 0,0 (CPOL = 0, CPHA = 0) and Mode 1,1 (CPOL = 1, CPHA = 1) as defined in the Functional Description section. Data is sampled on the first rising edge of SCK after CS goes low in Mode 0,0, and on the first falling edge in Mode 1,1. The 25AA256-E/MF does not auto-detect mode; the host MCU must configure its SPI peripheral accordingly before initiating communication.

How does the HOLD function behave during an active write cycle in the 25AA256-E/MF?

The HOLD pin has no effect during an internal write cycle (TWC) in the 25AA256-E/MF. Once CS rises after a valid WRITE command, the device enters self-timed 5 ms write mode, and HOLD is ignored until the write completes. During this time, SO remains high-impedance and all inputs except CS are masked. The HOLD function only operates during active SPI transfers (i.e., while CS is low and SCK is toggling).

Can the 25AA256-E/MF be used as a direct replacement for the 25LC256-I/MF on an existing PCB?

No - although both share the same 8-lead DFN (MF) package and pinout, the 25AA256-E/MF has different VCC min (1.8 V vs. 2.5 V) and temperature grade (AEC-Q100 Grade 1 vs. Industrial I-temp). Electrical behavior at <2.5 V and reliability at 125°C ambient are not guaranteed for the 25LC256-I/MF. Substituting requires validation of power rail stability, timing margins, and thermal derating - the 25AA256-E/MF is not a drop-in replacement without design review.

What happens to the write enable latch (WEL) after a successful WRITE command in the 25AA256-E/MF?

In the 25AA256-E/MF, the write enable latch (WEL) is automatically reset to '0' upon completion of any successful WRITE, WRSR, or WRDI instruction - including after the internal write cycle (TWC) finishes. This means each write operation requires a fresh WREN instruction. Power-up, CS high between commands, and execution of WRDI or WRSR also clear WEL. This behavior prevents unintended writes and enforces explicit enable discipline in safety-critical firmware.