Microchip Technology 25AA040-I/P

Overview

25AA040-I/P from Microchip Technology Inc. is a 4 Kbit (512 × 8) SPI-compatible serial EEPROM with 1.8–5.5 V supply range, 1 MHz max clock frequency, and industrial temperature rating (–40°C to +85°C). It features 16-byte page write capability, hardware write protection via WP pin, and HOLD functionality for interrupt-safe bus suspension. Used in embedded systems for firmware storage, calibration data retention, and configuration parameter backup.

For engineers reviewing the 25AA040-I/P datasheet, 25AA040-I/P pinout, 25AA040-I/P application, or 25AA040-I/P equivalent, key selection criteria include low-voltage operation (1.8 V min), 500 nA standby current, 1M endurance cycles, and PDIP-8 packaging for through-hole prototyping and legacy industrial control designs.

Technical Context

The 25AA040-I/P implements a standard SPI Mode 0,0 interface with separate SI (data in) and SO (data out) lines, requiring CS, SCK, WP, and HOLD control signals. Its internal architecture includes a write-enable latch, STATUS register with WIP/WEL/BP bits, and block protection logic enabling selective 0%, 25%, 50%, or 100% array write-lock.

It supports byte and page write operations with self-timed 5 ms internal write cycle, sequential read with automatic address increment, and power-on reset of the write-enable latch. The HOLD pin suspends ongoing transfers without resetting the internal state, allowing host MCU to service higher-priority interrupts while preserving transaction context.

Key Specifications

Pinout & Package

25AA040-I/P is supplied in an 8-pin Plastic Dual In-line Package (PDIP) with 300 mil body width, compatible with standard through-hole PCB assembly and manual prototyping. Pin 1 is marked with a notch or dot; orientation follows JEDEC MS-001 standard.

Key Features

Applications

Equivalent & Alternatives

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

Compared with 25AA040-I/P, 25AA040A-I/P offers identical functionality with improved reliability and supply longevity, while AT25040B-PU trades 1.8 V operation and HOLD support for higher speed and SOIC-only availability - making each alternative optimal for distinct design priorities.

Availability

25AA040-I/P is available at Aetrix Electronics and suitable for industrial sensor calibration, medical device configuration, smart energy meter firmware patch storage, and automotive body control module settings requiring stable component supply across extended product lifecycles.

Supply support for 25AA040-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 microcontroller, analog, FPGA, and memory solutions, headquartered in Chandler, Arizona, with global design and manufacturing operations.

The 25AA040-I/P belongs to Microchip's legacy SPI Serial EEPROM product line, designed specifically for cost-sensitive, low-power embedded systems requiring simple, robust nonvolatile storage with minimal external components.

FAQ

What is the operating voltage range of the 25AA040-I/P?

The 25AA040-I/P operates from 1.8 V to 5.5 V, enabling direct integration with 1.8 V, 3.3 V, and 5 V microcontroller systems without level translation. This wide range is confirmed in the Device Selection Table and DC Characteristics section of DS21204E, where VCC min is specified as 1.8 V for the 25AA040 variant.

Does the 25AA040-I/P support page write operations?

Yes, the 25AA040-I/P supports 16-byte page write operations, as stated in the Features section and verified in Section 3.3 (Write Sequence). Up to 16 bytes can be written in a single transaction if they reside within the same page boundary (XXXX0000–XXXX1111), reducing total write cycles compared to byte-by-byte programming.

How does the HOLD pin function on the 25AA040-I/P?

The HOLD pin on the 25AA040-I/P pauses ongoing SPI communication without resetting the internal address pointer or command state. When pulled low while SCK is low, it tri-states SO and ignores SI/SCK transitions, allowing the host MCU to service interrupts and resume exactly where the transfer left off - a feature explicitly documented in Section 2.6 and Figure 1-1.

What is the maximum clock frequency supported by the 25AA040-I/P?

The 25AA040-I/P supports up to 1 MHz maximum clock frequency when VCC is 4.5–5.5 V, as defined in the Device Selection Table and AC Characteristics (Table 1-2, Param No. 1). Frequency derates to 2 MHz for 25LC040 and 3 MHz for 25C040, confirming 1 MHz is the correct limit for this specific part number.

Is the 25AA040-I/P suitable for new designs?

No - the official Microchip datasheet (DS21204E, page 1) states "Not recommended for new designs – Please use 25AA040A or 25LC040A." The 25AA040-I/P remains fully supported for legacy repair, continuity builds, and existing production, but 25AA040A-I/P is the designated replacement with enhanced ESD and long-term supply assurance.