Microchip Technology 25AA040AT-I/SN

Overview

25AA040AT-I/SN from Microchip Technology Inc. is a 4 Kbit SPI Serial EEPROM with 512 × 8-bit organization, 1.8–5.5 V supply range, and industrial temperature rating (–40°C to +85°C). It supports up to 10 MHz clock frequency, 16-byte page write mode, and hardware write protection via WP pin. Used for nonvolatile parameter storage in microcontroller-based embedded systems requiring low-power, reliable data retention.

For engineers reviewing the 25AA040AT-I/SN datasheet, 25AA040AT-I/SN pinout, 25AA040AT-I/SN application, or 25AA040AT-I/SN equivalent, key selection criteria include SPI interface compatibility, 16-byte page boundary handling, HOLD/CS timing margins at 1.8 V, and block protection configuration via STATUS register BP0/BP1 bits.

Technical Context

The 25AA040AT-I/SN implements a standard SPI Mode 0,0 (CPOL = 0, CPHA = 0) interface with separate SI/SO lines and active-low CS. It uses an internal high-voltage generator for EEPROM programming and includes a status register with WIP, WEL, BP0, and BP1 bits for real-time write monitoring and configurable 0%, 25%, 50%, or 100% array protection.

Write operations require explicit WREN instruction followed by CS high-to-low transition to initiate self-timed internal write cycle (≤5 ms). HOLD pin suspends serial communication while preserving internal state, enabling interrupt servicing without sequence restart - critical in real-time MCU firmware with tight timing constraints.

Key Specifications

Pinout & Package

25AA040AT-I/SN is packaged in an 8-lead SOIC (SN) with 150 mil width, RoHS-compliant matte tin finish, and standard JEDEC MS-012AC footprint (5.3 mm × 5.3 mm × 1.75 mm).

Key Features

Applications

Equivalent & Alternatives

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

Compared with 25LC040AT-I/SN and AT25040B-MAU-Y, the 25AA040AT-I/SN uniquely supports 1.8 V operation while retaining HOLD and full BP0/BP1 block protection - making it the only drop-in solution for low-voltage, interrupt-aware, and safety-critical applications.

Availability

25AA040AT-I/SN is available at Aetrix Electronics and suitable for industrial sensor calibration, medical device configuration, automotive body control modules, and smart energy meter firmware patch storage requiring stable component supply across extended product lifecycles.

Supply support for 25AA040AT-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, FPGA, and memory solutions, headquartered in Chandler, Arizona, with global design and manufacturing operations.

The 25AA040A family was designed specifically for robust, low-voltage SPI EEPROM applications in industrial, medical, and automotive systems where data integrity, long-term retention, and hardware-level write protection are mandatory.

FAQ

What is the minimum VCC voltage supported by the 25AA040AT-I/SN?

The 25AA040AT-I/SN operates down to 1.8 V, enabling direct interface with 1.8 V microcontrollers and low-power sensor nodes without level-shifting circuitry. This is confirmed in the DC Characteristics table (D010–D012) and Device Selection Table, distinguishing it from the 25LC040A variant which requires ≥2.5 V.

How does the HOLD pin function during an active SPI transaction on the 25AA040AT-I/SN?

The HOLD pin on the 25AA040AT-I/SN pauses serial communication mid-transaction when asserted low (with SCK low), placing SI, SO, and SCK in high-impedance states while preserving the internal address pointer and command state. Resuming requires bringing HOLD high while SCK remains low - ensuring deterministic re-entry without sequence restart.

Can the 25AA040AT-I/SN perform page writes across 16-byte boundaries?

No. The 25AA040AT-I/SN restricts page writes to within a single 16-byte physical page (e.g., 0x00–0x0F, 0x10–0x1F). Attempting to write across a boundary causes wraparound to the start of the current page, overwriting prior data. Application firmware must enforce page-aligned writes or split multi-page transfers manually.

What protection mechanisms prevent unintended writes to the 25AA040AT-I/SN memory array?

The 25AA040AT-I/SN employs four layered protections: (1) Power-on reset of the write enable latch, (2) Explicit WREN instruction required before each write, (3) Hardware WP pin that disables all writes when low, and (4) Configurable BP0/BP1 bits in the STATUS register to lock 0%, 25%, 50%, or 100% of the array - all verified in Sections 2.4, 2.7, and Table 2-3 of DS21827H.

Is the 25AA040AT-I/SN pin-compatible with other Microchip 4 Kbit SPI EEPROMs like the 25LC040A?

Yes - the 25AA040AT-I/SN shares identical 8-lead SOIC (SN) pinout, signal definitions, and timing with the 25LC040AT-I/SN. However, due to its 1.8 V minimum VCC, it is not functionally interchangeable in 2.5 V-only systems where the 25LC040A is specified; electrical compatibility must be validated per application voltage rails.