Microchip Technology 25AA040AXT-I/ST

Overview

25AA040AXT-I/ST 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 25AA040AXT-I/ST datasheet, 25AA040AXT-I/ST pinout, 25AA040AXT-I/ST application, or 25AA040AXT-I/ST equivalent, key selection criteria include SPI interface compatibility, 1.8 V minimum VCC operation, page-write timing constraints, and hardware block protection configuration using BP0/BP1 bits in the STATUS register.

Technical Context

The 25AA040AXT-I/ST implements a standard SPI Mode 0,0/Modes 1,1-compatible serial interface with separate SI (data in) and SO (data out) lines, controlled by CS, SCK, and optional HOLD. It uses an internal 8-bit instruction register and supports MSb-first transmission of instructions, addresses, and data.

Write operations require explicit WREN instruction followed by CS high-to-low transition to initiate self-timed internal write cycle (≤5 ms), with automatic WEL reset post-write. Block protection is configured nonvolatily via WRSR instruction to protect none, 1/4, 1/2, or all memory array segments.

Key Specifications

Pinout & Package

25AA040AXT-I/ST is supplied in an 8-lead TSSOP package (ST suffix), with pin 1 marked by laser dot. Package dimensions: 4.4 mm × 3.0 mm × 1.2 mm, lead pitch 0.65 mm, RoHS-compliant matte tin finish.

Key Features

Applications

Equivalent & Alternatives

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

Compared with 25LC040AT-I/ST and AT25040B-SSHL-T, the 25AA040AXT-I/ST uniquely supports 1.8 V operation while maintaining industrial temperature range and identical TSSOP-8 footprint - making it optimal for space-constrained, ultra-low-voltage embedded designs.

Availability

25AA040AXT-I/ST is available at Aetrix Electronics and suitable for industrial sensor calibration, medical device configuration, and automotive body control modules requiring stable component supply across multi-year production cycles.

Supply support for 25AA040AXT-I/ST 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, and Flash-IP solutions, headquartered in Chandler, Arizona, with global design and manufacturing operations.

The 25AA040A family was designed specifically for cost-sensitive, low-power embedded systems needing reliable SPI EEPROM with wide VCC range and hardware write protection - targeting industrial, medical, and automotive subsystems.

FAQ

What is the minimum supply voltage required for reliable operation of the 25AA040AXT-I/ST?

The 25AA040AXT-I/ST operates reliably from 1.8 V to 5.5 V. At 1.8 V, maximum clock frequency is reduced to 3 MHz, and AC timing parameters such as TCSS and TV are relaxed per Table 1-2. All DC characteristics including read/write current and standby current remain specified across this full range, enabling direct integration into 1.8 V logic domains without level-shifting.

Does the 25AA040AXT-I/ST support page write across memory boundaries?

No, the 25AA040AXT-I/ST does not support page writes across physical page boundaries. Each page is 16 bytes (addresses ending in 0x00–0x0F, 0x10–0x1F, etc.). Attempting a page write that crosses a boundary causes wraparound within the current page, overwriting earlier bytes. Application firmware must validate address alignment prior to issuing WRITE commands to prevent unintended data loss in the 25AA040AXT-I/ST.

How does the HOLD pin function during an active SPI transaction in the 25AA040AXT-I/ST?

The HOLD pin in the 25AA040AXT-I/ST suspends SPI communication mid-sequence when pulled low while SCK is low. During HOLD, SI, SCK, and SO enter high-impedance states and all inputs except CS are ignored. The internal address pointer and instruction state are preserved. Resuming requires bringing HOLD high while SCK remains low; the 25AA040AXT-I/ST then continues from the exact point of suspension without retransmission.

Can the WP pin override software write protection settings in the 25AA040AXT-I/ST?

Yes, the WP pin has priority over software-controlled write protection. When WP is low, all writes to memory and the STATUS register are disabled regardless of BP0/BP1 or WEL bit states. This hardware lock cannot be overridden by WREN, WRSR, or any instruction. The 25AA040AXT-I/ST datasheet confirms this behavior in Table 2-4: WP = 0 forces full protection even if WEL = 1 and BP bits permit writes.

What is the typical duration of an internal write cycle for the 25AA040AXT-I/ST?

The internal write cycle for the 25AA040AXT-I/ST completes in ≤5 ms after CS rises following a valid WRITE or WRSR command. This time is fixed and independent of byte count (single-byte or full 16-byte page). During this period, the WIP bit in the STATUS register reads '1'; polling this bit is the recommended method to detect write completion before initiating subsequent operations on the 25AA040AXT-I/ST.