Microchip Technology 25AA256-I/SN

Overview

25AA256-I/SN from Microchip Technology is a 256 Kbit (32,768 × 8) SPI serial EEPROM with 1.8–5.5 V supply range, 64-byte page write capability, and industrial temperature rating (–40°C to +85°C). It features hardware write protection via WP pin and STATUS register, self-timed 5 ms max write cycles, and supports microcontroller-based data logging in embedded control systems.

For engineers reviewing the 25AA256-I/SN datasheet, 25AA256-I/SN pinout, 25AA256-I/SN application, or 25AA256-I/SN equivalent, key selection criteria include its 10 MHz max SPI clock at 4.5–5.5 V, 1 µA standby current, AEC-Q100 qualification, and SOIC-8 (SN) package compatibility with legacy PCB footprints.

Technical Context

The 25AA256-I/SN implements a standard SPI Mode 0,0 interface with separate SI (data-in) and SO (data-out) lines, requiring CS, SCK, and HOLD for full protocol support. Its internal architecture includes a write-enable latch, nonvolatile STATUS register (BP0/BP1/WEL/WIP), and page latches enabling burst writes within 64-byte boundaries.

Write operations require explicit WREN instruction followed by CS high-to-low transition to initiate internal 5 ms erase/write cycle; during this time, RDSR allows polling of WIP bit while array reads are blocked. Hardware write protection engages only when WPEN=1 and WP=low, leaving other functions fully operational.

Key Specifications

Pinout & Package

25AA256-I/SN is packaged in an 8-lead narrow SOIC (SN) with 1.27 mm pitch, 3.90 mm body width, and JEDEC MS-012AC compliant footprint. Pin 1 is marked with a beveled corner or dot; device orientation follows standard SOIC conventions.

Key Features

Applications

Equivalent & Alternatives

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

Compared with 25LC256-I/SN and AT25DF256A-SSH-T, the 25AA256-I/SN uniquely supports 1.8 V operation and HOLD pin pausing - critical for ultra-low-power and real-time deterministic systems where voltage scaling and interrupt latency matter.

Availability

25AA256-I/SN is available at Aetrix Electronics and suitable for industrial automation, medical instrumentation, and automotive electronics requiring stable component supply across extended temperature ranges and long product lifecycles.

Supply support for 25AA256-I/SN 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 devices, and memory solutions, headquartered in Chandler, Arizona, with global design and manufacturing operations.

The 25AA256 belongs to Microchip's serial EEPROM product line, engineered for reliable, low-power nonvolatile storage in space-constrained embedded systems where SPI interface simplicity and AEC-Q100 qualification are mandatory.

FAQ

What is the minimum supply voltage supported by the 25AA256-I/SN?

The 25AA256-I/SN operates down to 1.8 V, enabling direct integration with modern ultra-low-power microcontrollers and battery-powered sensors without level-shifting circuitry. This 1.8 V minimum distinguishes it from the 25LC256 variant, which requires ≥2.5 V. Operation at 1.8 V maintains full functionality including 5 ms write cycles and STATUS register access, though maximum SPI clock rate reduces to 3 MHz per AC specifications.

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

The HOLD pin on the 25AA256-I/SN suspends ongoing SPI communication when pulled low while SCK is low, preserving the internal address pointer and command state. All inputs except CS are ignored during hold, and SO enters high-impedance. Resuming requires bringing HOLD high while SCK remains low; the transaction continues from the exact bit position where it paused. This enables deterministic interrupt handling in RTOS environments without retransmitting commands.

Can the 25AA256-I/SN be used as a drop-in replacement for the 25LC256-I/SN?

No - while pinout and instruction set are identical, the 25AA256-I/SN supports 1.8–5.5 V operation versus 25LC256-I/SN's 2.5–5.5 V range. Substituting into a 2.5 V system is safe, but using 25LC256-I/SN in a 1.8 V design will cause functional failure. Always verify VCC compliance and validate timing margins at the actual operating voltage before substitution.

What protection mechanisms prevent unintended writes to the 25AA256-I/SN memory array?

The 25AA256-I/SN employs four layered protections: (1) Power-on reset clears the write-enable latch; (2) Explicit WREN instruction required before any write; (3) Write-enable latch auto-resets after each WRITE, WRSR, or WRDI command; (4) Hardware WP pin blocks STATUS register writes when WPEN=1 and WP=low. These ensure that noise spikes, brown-outs, or software bugs cannot corrupt stored data without deliberate multi-step activation.

Is the 25AA256-I/SN RoHS compliant and halogen-free?

Yes - the 25AA256-I/SN is RoHS compliant per Directive 2011/65/EU and halogen-free per IPC-4101D requirements. Package marking includes the "3e" RoHS identifier, and material declarations confirm <900 ppm bromine and <900 ppm chlorine content. This compliance is verified through Microchip's certified supply chain and third-party lab testing per IEC 62321 standards.