Microchip Technology 25AA256/WF16K

Overview

25AA256/WF16K 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 automotive 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, industrial sensor nodes, and medical device configuration storage.

For engineers reviewing the 25AA256/WF16K datasheet, 25AA256/WF16K pinout, 25AA256/WF16K application, or 25AA256/WF16K equivalent, key selection criteria include V_CC min (1.8 V), page size (64 B), endurance (1M cycles), data retention (>200 years), and SPI timing compliance across voltage/temperature grades.

Technical Context

The 25AA256/WF16K implements a standard SPI Mode 0,0 / Mode 1,1 interface with separate SI/SO lines, CS-controlled selection, and HOLD-driven pause/resume capability. Its internal architecture includes an 8-bit instruction register, page latches, HV generator for EEPROM programming, and a STATUS register with WIP, WEL, BP0/BP1, and WPEN bits.

Write operations require explicit WREN instruction followed by CS high-to-low transition to initiate internal 5 ms erase/write cycle; page writes are bounded to 64-byte physical boundaries and wrap on overflow. Block protection supports four configurations (none, upper 1/4, upper 1/2, or full array) via nonvolatile BP bits programmed through WRSR.

Key Specifications

Pinout & Package

25AA256/WF16K is packaged in an 8-lead SOIC (SN) with 150-mil body width, JEDEC MS-012AC compliant footprint, and matte tin (Sn) lead finish. Pin 1 is marked by a beveled corner or dot; package dimensions: 4.90 mm × 3.90 mm × 1.25 mm (L × W × H).

Key Features

Applications

Equivalent & Alternatives

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

Compared with 25LC256-I/P, 25AA256/WF16K adds 1.8 V operation and AEC-Q100 qualification but shares identical package and SPI protocol; versus AT25DF256A-SSH-T, it offers pin-compatible simplicity and HOLD support at lower speed, making it preferable for cost-sensitive, interrupt-aware embedded control.

Availability

25AA256/WF16K is available at Aetrix Electronics and suitable for automotive engine control units, industrial sensor nodes, medical infusion pumps, and smart meter firmware storage requiring stable component supply across extended temperature and long-lifecycle programs.

Supply support for 25AA256/WF16K 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/WF16K belongs to Microchip's serial EEPROM product line, engineered for robust, low-power nonvolatile data storage in automotive, industrial, and medical applications demanding high endurance and long-term data integrity.

FAQ

What is the minimum supply voltage required for reliable operation of the 25AA256/WF16K?

The 25AA256/WF16K operates reliably down to 1.8 V across its full temperature range (−40°C to +125°C). At V_CC = 1.8 V, maximum clock frequency is 3 MHz, and write current is reduced to 0.15 mA. This enables direct interfacing with 1.8 V logic families without level shifters - a key differentiator from the 25LC256, which requires ≥2.5 V.

How does the HOLD pin function during an active SPI transaction on the 25AA256/WF16K?

The HOLD pin on the 25AA256/WF16K suspends SPI communication mid-sequence without resetting the internal state. When pulled low while SCK is low, SI/SO/SCK inputs are ignored and SO enters high-impedance. To resume, HOLD must be raised while SCK remains low; the transaction continues from the exact bit position where it paused - essential for servicing time-critical interrupts in real-time systems using the 25AA256/WF16K.

Can the 25AA256/WF16K be used as a direct replacement for the 25LC256 in an existing design?

The 25AA256/WF16K is pin-compatible and functionally identical to the 25LC256 in all respects except supply voltage range: it supports 1.8–5.5 V versus 2.5–5.5 V. If the host system operates ≥2.5 V, the 25AA256/WF16K can replace the 25LC256 without hardware change. However, if the design relies on 25LC256's higher minimum V_CC for noise margin, verify timing margins at 2.5 V using the 25AA256/WF16K's AC specs.

What protection mechanisms prevent unintended writes to the 25AA256/WF16K memory array?

The 25AA256/WF16K employs three layered protections: (1) a volatile write-enable latch (WEL) that resets on power-up and after every write; (2) nonvolatile block protection (BP0/BP1) configurable via WRSR to lock 0%, 25%, 50%, or 100% of memory; and (3) hardware write protection via WP pin + WPEN bit, which permanently disables STATUS register writes when enabled - all enforced independently in the 25AA256/WF16K.

Is the 25AA256/WF16K suitable for automotive applications requiring AEC-Q100 certification?

Yes, the 25AA256/WF16K is explicitly qualified to AEC-Q100 Grade 1 (−40°C to +125°C) and listed in Microchip's official AEC-Q100 documentation. It undergoes stress testing including HTOL, temperature cycling, and ESD (>4 kV HBM), making it approved for use in engine control modules, transmission controllers, and other under-hood automotive systems - a certified attribute of the 25AA256/WF16K, not inferred.