Microchip Technology AT25256AW-10SU-1.8

Overview

AT25256AW-10SU-1.8 from Microchip Technology (formerly Atmel) is a 256 Kbit SPI serial EEPROM organized as 32,768 × 8 bits, operating from 1.8 V to 5.5 V, supporting 20 MHz clock rate at 5 V, featuring 64-byte page write, block write protection (1/4, 1/2, or full array), and 1 million write cycles endurance. It serves as nonvolatile configuration storage in industrial sensor nodes and embedded control modules requiring low-voltage operation.

For engineers reviewing the AT25256AW-10SU-1.8 datasheet, AT25256AW-10SU-1.8 pinout, AT25256AW-10SU-1.8 application, or AT25256AW-10SU-1.8 equivalent, key selection criteria include 1.8 V minimum supply compatibility, SOIC-8 (EIAJ) package footprint, SPI Mode 0/3 support, hardware write protection via WP pin, and automotive-grade temperature range (−40°C to +85°C).

Technical Context

The AT25256AW-10SU-1.8 implements a synchronous serial peripheral interface (SPI) with dedicated SI (input), SO (output), SCK (clock), CS (chip select), WP (write protect), and HOLD (communication suspend) pins. It operates exclusively as a slave device, requiring master-generated clock and obeying op-codes including WREN, WRITE, RDSR, and WRSR for memory access and status control.

Internal architecture includes an 8-bit instruction register, nonvolatile status register (BP0/BP1/WPEN/WEN/RDY bits), and automatic address increment during sequential read/write. Write cycles are self-timed (≤5 ms), require prior WREN activation, and support page-mode writes up to 64 bytes without external erase-enabling efficient firmware parameter updates in resource-constrained systems.

Key Specifications

Pinout & Package

AT25256AW-10SU-1.8 uses an 8-lead EIAJ SOIC package (package code "S2", body width 0.209", JEDEC MS-012 compliant), with 1.27 mm pitch, 5.13–5.35 mm length, and 7.70–8.26 mm width. Pin 1 is marked by a beveled corner or notch.

Key Features

Applications

Equivalent & Alternatives

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

Compared with M95256-DW and BR25H256FJ-10, AT25256AW-10SU-1.8 uniquely balances 1.8 V operation, 20 MHz performance, HOLD capability, and EIAJ SOIC-8 footprint-making it optimal for space-constrained, battery-powered industrial controllers needing flexible communication suspension and wide supply tolerance.

Availability

AT25256AW-10SU-1.8 is available at Aetrix Electronics and suitable for industrial sensor calibration, medical device configuration, automotive body control modules, and smart energy meter firmware requiring stable component supply across extended temperature ranges and long product lifecycles.

Supply support for AT25256AW-10SU-1.8 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 acquired Atmel in 2016 and maintains its serial EEPROM portfolio, emphasizing robustness, longevity, and industrial-grade reliability in nonvolatile memory solutions.

The AT25256A family was designed for embedded systems requiring low-power, low-voltage serial configuration storage with hardware-enforced write protection-targeting industrial automation, medical instrumentation, and automotive subsystems.

FAQ

What is the minimum supply voltage supported by AT25256AW-10SU-1.8?

The AT25256AW-10SU-1.8 supports a minimum supply voltage of 1.8 V, enabling direct integration with 1.8 V logic families and low-power microcontrollers. Operation below 1.8 V is not guaranteed and may result in unreliable read/write behavior or status register corruption. The device remains fully functional across the full 1.8 V to 5.5 V range, with timing specifications validated down to 1.8 V per Table 1-2 and Table 1-3 in the datasheet. AT25256AW-10SU-1.8 maintains 20 MHz clock capability only at VCC ≥ 4.5 V; at 1.8 V, maximum SCK frequency is 5 MHz.

Does AT25256AW-10SU-1.8 support SPI Mode 3, and how is it configured?

Yes, AT25256AW-10SU-1.8 explicitly supports SPI Mode 3 (CPOL = 1, CPHA = 1), where SCK idles high and data is sampled on the falling edge. No hardware configuration is required-the device automatically interprets clock polarity and phase based on master timing. Mode 0 (CPOL = 0, CPHA = 0) is the default and most commonly used; Mode 3 support expands compatibility with legacy or specialized MCUs. AT25256AW-10SU-1.8 does not require mode-select pins or status register bits to enable Mode 3-it is inherent to the SPI interface design per the datasheet's "SPI Modes 0 (0,0) and 3 (1,1)" specification.

How does the HOLD pin function during an active SPI transaction on AT25256AW-10SU-1.8?

The HOLD pin on AT25256AW-10SU-1.8 suspends serial communication without resetting the internal address counter or command state. To activate HOLD, the pin must be driven low while SCK is low; the SO pin immediately enters high-impedance, and SI inputs are ignored. Communication resumes when HOLD is returned high while SCK remains low-ensuring deterministic restart. This allows a master MCU to pause EEPROM access during higher-priority interrupts. AT25256AW-10SU-1.8 retains all pending data and address context, making HOLD ideal for real-time systems where bus arbitration is critical.

What protection mechanisms prevent unintended writes to AT25256AW-10SU-1.8?

AT25256AW-10SU-1.8 employs three independent write protection layers: (1) Software-based WREN instruction requirement before any write, (2) Status register BP0/BP1 bits enabling 1/4, 1/2, or full-array hardware lock, and (3) WP pin assertion (low) combined with WPEN bit set to "1" to inhibit status register and protected memory writes. All three can operate simultaneously-for example, WP=low + WPEN=1 blocks status changes even if WREN is issued, while BP bits restrict memory access regardless of WP state. AT25256AW-10SU-1.8 ensures that unprotected regions remain writable only when all three conditions are satisfied.

Is AT25256AW-10SU-1.8 pin-compatible with other packages in the AT25256A family?

AT25256AW-10SU-1.8 is pin-compatible with all 8-pin variants of the AT25256A family-including PDIP-8, SOIC-8 (JEDEC and EIAJ), TSSOP-8, dBGA2-8, and SAP-8-because all share identical pin numbering and function mapping (CS, SO, WP, GND, VCC, HOLD, SCK, SI). The "W" in the part number denotes EIAJ SOIC-8 (8S2), but electrical and logical behavior is identical across packages. Mechanical differences (body size, lead pitch, thermal profile) require PCB layout adaptation, but schematic symbols and firmware drivers remain unchanged. AT25256AW-10SU-1.8 thus enables drop-in replacement across form factors when board space or assembly constraints change.