Microchip Technology 25AA256T-I/SM

Overview

25AA256T-I/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 at 5.5 V, delivers ≤5 mA write current, and offers >200-year data retention. It serves as nonvolatile configuration storage in microcontroller-based industrial control modules requiring robust, low-power, AEC-Q100-qualified memory.

For engineers reviewing the 25AA256T-I/SM datasheet, 25AA256T-I/SM pinout, 25AA256T-I/SM application, or 25AA256T-I/SM equivalent, key selection criteria include its 1.8 V minimum operating voltage, hardware write protection via WP pin and STATUS register, HOLD functionality for interrupt-safe SPI pauses, and automotive-grade temperature support (–40°C to +85°C).

Technical Context

The 25AA256T-I/SM implements a standard SPI Mode 0,0 or Mode 1,1 interface with separate SI (data in) and SO (data out) lines, controlled by CS, SCK, and optional HOLD. Its internal architecture includes an 8-bit instruction register, page latches, and high-voltage generator for EEPROM programming.

Write operations require explicit WREN instruction followed by CS high-to-low transition to initiate self-timed internal write cycles (≤5 ms). Block protection is configurable via BP0/BP1 bits to lock 0%, 25%, 50%, or 100% of the 32 KB array, while WPEN enables hardware-level write-disable when WP is low.

Key Specifications

Pinout & Package

25AA256T-I/SM uses an 8-lead SOIC package (SN/SM suffix), measuring 3.90 mm × 4.90 mm × 1.25 mm (body height), with gull-wing leads and JEDEC-standard footprint.

Key Features

Applications

Equivalent & Alternatives

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

Compared with 25AA256T-I/SM, 25LC256-I/SN trades 1.8 V operation for identical industrial-grade functionality, while AT25DF256A-SSH-T offers higher density and speed at the cost of interface compatibility and voltage flexibility - making 25AA256T-I/SM optimal for cost-sensitive, low-voltage, automotive-qualified embedded systems.

Availability

25AA256T-I/SM is available at Aetrix Electronics and suitable for industrial PLCs, automotive sensor modules, medical diagnostics loggers, and smart meter firmware storage requiring stable component supply across multi-year production cycles.

Supply support for 25AA256T-I/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 U.S.-based semiconductor manufacturer specializing in microcontrollers, analog devices, and memory solutions, with global design centers and ISO 9001-certified manufacturing.

The 25AA256T-I/SM belongs to Microchip's 25XX256 serial EEPROM product line, engineered for reliable, low-power, SPI-based nonvolatile storage in automotive, industrial, and medical applications demanding AEC-Q100 validation and extended data retention.

FAQ

What is the minimum supply voltage required for reliable operation of the 25AA256T-I/SM?

The 25AA256T-I/SM operates reliably down to 1.8 V, enabling direct integration with modern ultra-low-power microcontrollers without external level-shifting circuitry. At this voltage, maximum clock frequency is reduced to 3 MHz, and AC timing parameters such as TCSS and TCSH scale accordingly per Table 1-2. This specification is verified across the full industrial temperature range (–40°C to +85°C).

How does the HOLD pin function during an active SPI transaction with the 25AA256T-I/SM?

The HOLD pin suspends ongoing SPI communication without resetting the internal state of the 25AA256T-I/SM. When asserted low while SCK is low, SI, SCK, and SO enter high-impedance states and all inputs except CS are ignored. To resume, HOLD must be returned high while SCK remains low; the transaction continues from the exact bit position where it paused. This allows host MCUs to service urgent interrupts without data loss or re-synchronization overhead.

Can the 25AA256T-I/SM be used in automotive applications, and what qualifications does it hold?

Yes, the 25AA256T-I/SM is AEC-Q100 qualified for automotive applications, specifically rated for the Industrial temperature range (–40°C to +85°C). Its qualification covers stress testing for thermal cycling, humidity, and electrical robustness, making it suitable for use in body control modules, HVAC actuators, and sensor interfaces where data integrity and long-term reliability are critical.

What happens if a page write command crosses a 64-byte boundary in the 25AA256T-I/SM?

If a page write command attempts to cross a 64-byte physical page boundary, data wraps around to the start of the same page instead of advancing to the next page. For example, writing 10 bytes starting at address 0x003E overwrites bytes at 0x003E–0x003F and then 0x0000–0x0007. This behavior is inherent to the 25AA256T-I/SM's page latch architecture and requires firmware to enforce page-aligned writes or split multi-page transfers manually.

How is hardware write protection implemented on the 25AA256T-I/SM?

Hardware write protection on the 25AA256T-I/SM requires both the WP pin to be driven low and the WPEN bit (bit 7 of STATUS register) to be set high. When both conditions are met, writes to nonvolatile STATUS register bits (BP0, BP1, WPEN) are blocked - preventing accidental changes to block protection settings. All other operations, including memory reads and writes, remain fully functional unless additionally restricted by BP bits.