Microchip Technology 25AA040A-I/P

Overview

25AA040A-I/P 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, and hardware write protection via WP pin. Used for nonvolatile parameter storage in microcontroller-based embedded systems requiring low-power, high-reliability data retention.

For engineers reviewing the 25AA040A-I/P datasheet, 25AA040A-I/P pinout, 25AA040A-I/P application, or 25AA040A-I/P equivalent, key selection criteria include SPI interface compatibility, 1.8 V minimum VCC operation, page-write timing constraints, and hardware/software write-protection configuration across industrial-temperature designs.

Technical Context

The 25AA040A-I/P implements a standard SPI Mode 0,0 (CPOL = 0, CPHA = 0) interface with separate SI and SO lines, CS-controlled selection, and HOLD input for transaction suspension. Its internal architecture includes a 512-byte EEPROM array, page latches, status register with WIP/WEL/BP bits, and HV generator for write/erase cycles.

It features self-timed internal write cycles (≤5 ms), block write protection (none/¼/½/all), power-on write-disable latch reset, and dual-level write protection combining WP pin assertion and STATUS register BP0/BP1 bits - enabling flexible, layered data integrity control in resource-constrained systems.

Key Specifications

Pinout & Package

25AA040A-I/P is supplied in 8-lead PDIP (Plastic Dual In-line Package) with 0.3-inch body width, RoHS-compliant matte tin plating, and industrial-grade marking (e.g., "I/P 1L7" and date code). Pin 1 is identified by notch or laser mark.

Key Features

Applications

Equivalent & Alternatives

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

Compared with 25AA040A-I/P, the 25LC040A-I/P offers identical functionality at higher minimum voltage, while the AT25040B-SSHL-T trades HOLD support and 1.8 V operation for faster clocking - making 25AA040A-I/P the sole choice for ultra-low-voltage, interrupt-aware, or WP-pin-dependent designs.

Availability

25AA040A-I/P is available at Aetrix Electronics and suitable for industrial control systems, medical diagnostics equipment, and consumer appliance designs requiring stable component supply, long-term manufacturability, and guaranteed RoHS compliance.

Supply support for 25AA040A-I/P 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 25AA040A belongs to Microchip's legacy SPI Serial EEPROM product line, engineered for robust, low-power, pin-efficient nonvolatile storage in cost-sensitive and reliability-critical embedded applications across industrial, medical, and consumer markets.

FAQ

What is the minimum supply voltage required for reliable operation of the 25AA040A-I/P?

The 25AA040A-I/P operates reliably down to 1.8 V across its full industrial temperature range (−40°C to +85°C). This 1.8 V minimum enables direct integration with low-voltage microcontrollers and battery-powered systems without level shifters. Operation below 1.8 V is not characterized and may result in undefined behavior or data corruption. The 25AA040A-I/P datasheet specifies DC characteristics only for VCC ≥ 1.8 V.

Does the 25AA040A-I/P support page write operations, and what is the maximum page size?

Yes, the 25AA040A-I/P supports page write mode with a fixed page size of 16 bytes. Up to 16 consecutive bytes can be loaded into the page buffer and written in a single internal cycle (≤5 ms). Writes crossing a 16-byte boundary wrap within the same page - so software must enforce alignment to prevent unintended overwrites. This capability significantly improves write efficiency versus byte-wise programming.

How does the HOLD pin function during an active SPI transaction on the 25AA040A-I/P?

The HOLD pin on the 25AA040A-I/P suspends an ongoing SPI sequence without resetting internal state. When pulled low while SCK is low, SI/SO/SCK inputs are ignored, SO goes high-impedance, and the address pointer and instruction context are preserved. Resuming requires bringing HOLD high while SCK remains low. This allows host MCUs to service time-critical interrupts and resume exactly where the transaction left off - a key advantage over software-only pause methods.

Can the 25AA040A-I/P be used in systems requiring write protection at both hardware and software levels?

Yes, the 25AA040A-I/P provides dual-layer write protection: hardware-level via the dedicated WP pin (low = all writes disabled), and software-configurable via the STATUS register BP0/BP1 bits (selecting none/¼/½/all array protection). These mechanisms operate independently - for example, WP = low overrides STATUS register settings, ensuring fail-safe protection even if firmware is compromised. This makes 25AA040A-I/P suitable for safety-critical parameter storage.

What is the endurance specification for the 25AA040A-I/P, and how is it validated?

The 25AA040A-I/P is rated for 1,000,000 erase/write cycles per memory location at 25°C and VCC = 5.5 V. This endurance is ensured by characterization (not 100% tested) and supported by Microchip's Total Endurance™ Model for application-specific lifetime estimation. Field reliability data confirms >200 years of data retention under typical operating conditions, making it appropriate for infrastructure equipment with multi-decade service life requirements.