Microchip Technology 25AA256-E/P

Overview

25AA256-E/P from Microchip Technology Inc. is a 256 Kbit (32,768 × 8) SPI Serial EEPROM with 1.8–5.5V supply range, 64-byte page write capability, and industrial/extended temperature support (–40°C to +125°C). It features hardware write protection via WP pin and STATUS register, HOLD functionality for interrupt-safe bus suspension, and is packaged in 8-lead PDIP. Used for nonvolatile configuration storage in embedded controllers and sensor nodes.

For engineers reviewing the 25AA256-E/P datasheet, 25AA256-E/P pinout, 25AA256-E/P application, or 25AA256-E/P equivalent, this page delivers verified electrical specs, SPI timing constraints across voltage ranges, real-world endurance (1M cycles), data retention (>200 years), and precise package-to-pin mapping for PDIP (P) variant - all confirmed from Microchip DS20001822H.

Technical Context

The 25AA256-E/P implements a standard SPI Mode 0,0/Master-Slave interface with separate SI/SO lines, CS-controlled selection, and SCK-synchronized data transfer (data latched on rising SCK edge, SO updated after falling edge). Its internal architecture includes a 64-byte page latch, HV generator for EEPROM programming, and status register with WIP/WEL/BP bits.

Write operations require explicit WREN instruction followed by CS high-to-low transition to initiate self-timed internal write cycle (≤5 ms); page writes are bounded within physical 64-byte pages and wrap on boundary violation. HOLD suspends ongoing serial transfers without resetting state, provided asserted while SCK is low.

Key Specifications

Pinout & Package

25AA256-E/P is supplied in 8-lead Plastic Dual In-Line Package (PDIP), 300 mil body width, with through-hole mounting and standard DIP footprint (Microchip drawing C04-018-P Rev E).

Key Features

Applications

Equivalent & Alternatives

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

Compared with 25LC256-I/P, the 25AA256-E/P enables 1.8V operation and extended temperature support; compared with AT25DF256A-SSH-T, it offers simpler command protocol and dedicated HOLD functionality for deterministic interrupt handling - making it optimal for resource-constrained, safety-critical embedded systems.

Availability

25AA256-E/P is available at Aetrix Electronics and suitable for industrial PLC configuration storage, automotive sensor calibration memory, medical device usage logs, and IoT edge node identity storage requiring stable component supply across extended temperature and long product lifecycles.

Supply support for 25AA256-E/P 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 U.S.-based semiconductor manufacturer specializing in microcontrollers, analog devices, and memory products, with a focus on reliability and long-term product availability.

The 25AA256-E/P belongs to Microchip's serial EEPROM product line, designed specifically for robust, low-power, SPI-based nonvolatile storage in automotive, industrial, and medical applications demanding AEC-Q100 qualification and >200-year data retention.

FAQ

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

The 25AA256-E/P operates reliably down to 1.8V, as specified in its DC characteristics table. This enables direct interfacing with 1.8V logic families and low-voltage battery-powered systems without level-shifting circuitry. Operation below 1.8V is not guaranteed and may result in undefined behavior or failed write cycles. The 25AA256-E/P datasheet confirms full functionality-including read, write, and status register access-across the entire 1.8–5.5V range.

Does the 25AA256-E/P support page write operations, and what is the maximum length?

Yes, the 25AA256-E/P supports page write operations with a fixed 64-byte page size. Up to 64 bytes can be written in a single transaction, provided all addresses reside within the same physical page boundary (e.g., 0x0000–0x003F). Attempting to cross a page boundary causes wraparound within the current page. The 25AA256-E/P datasheet explicitly defines this behavior in Section 2.3 and Table 2-3 to prevent unintended data overwrites.

How does the HOLD pin function during an active SPI transaction on the 25AA256-E/P?

The HOLD pin on the 25AA256-E/P suspends an ongoing SPI transaction without resetting internal state. When pulled low while SCK is low, SI/SO/SCK inputs are ignored and SO enters high-impedance. Communication resumes from the exact point of suspension when HOLD is returned high while SCK remains low. This behavior is fully documented in Figures 1-1 and Section 3.6 of the 25AA256-E/P datasheet for deterministic interrupt handling.

What write protection mechanisms are implemented in the 25AA256-E/P?

The 25AA256-E/P implements three layered write protections: (1) a volatile write-enable latch (WEL) reset on power-up, (2) nonvolatile block protection (BP0/BP1) enabling 0%/25%/50%/100% array lock, and (3) hardware write-protect via WP pin controlled by WPEN bit. These are detailed in Tables 2-2, 2-3, and the Write-Protect Functionality Matrix in the 25AA256-E/P datasheet, ensuring defense-in-depth against accidental or malicious writes.

Is the 25AA256-E/P qualified for automotive applications, and under which standard?

Yes, the 25AA256-E/P is explicitly qualified to AEC-Q100 Grade 1 (–40°C to +125°C), as stated in the Device Selection Table on page 1 of the 25AA256-E/P datasheet. This qualification covers stress testing for temperature cycling, humidity, ESD, and lifetime reliability-making it suitable for engine control, transmission, and ADAS modules where functional safety and long-term stability are mandatory.