Microchip Technology 25LC040AT-M/SN

Overview

25LC040AT-M/SN from Microchip Technology is a 4 Kbit (512 × 8) SPI Serial EEPROM with 2.5–5.5 V supply range, 16-byte page write capability, and industrial temperature grade (−40°C to +85°C). It features hardware write protection (WP pin), HOLD functionality for interrupt-safe bus suspension, and self-timed write cycles ≤5 ms. It is used in embedded systems for storing calibration data, configuration settings, and firmware parameters.

For engineers reviewing the 25LC040AT-M/SN datasheet, 25LC040AT-M/SN pinout, 25LC040AT-M/SN application, or 25LC040AT-M/SN equivalent, this page delivers verified electrical specs, SPI timing constraints, package mapping to SOIC-8 (SN), block protection behavior, and real-world use cases in industrial control and sensor modules.

Technical Context

The 25LC040AT-M/SN implements a standard SPI Mode 0,0 (CPOL=0, CPHA=0) interface with separate SI/SO lines and active-low CS. Its internal architecture includes a 512-byte EEPROM array, page latches, status register (WIP/WEL/BP0/BP1), and HV generator for write/erase operations.

It supports byte and page writes (up to 16 bytes within same 16-byte-aligned page), sequential read with automatic address increment, and hardware-based write protection via WP pin and BP bits. The HOLD pin suspends ongoing SPI transfers without resetting the sequence, enabling deterministic interrupt handling in real-time microcontroller systems.

Key Specifications

Pinout & Package

25LC040AT-M/SN is packaged in an 8-lead SOIC (SN) with 1.27 mm pitch, JEDEC MS-012AC compliant, and Pb-free/RoHS certified. Pin 1 is marked by laser dot or notch; exposed pad not present.

Key Features

Applications

Equivalent & Alternatives

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

Compared with 25LC040AT-M/SN, the 25AA040AT-I/SN extends voltage compatibility downward without sacrificing robustness, while the AT25040B-MAHL-T trades HOLD capability for higher clock rate - making each alternative optimal only under specific system-level timing and voltage constraints.

Availability

25LC040AT-M/SN is available at Aetrix Electronics and suitable for industrial control systems, sensor modules, and medical diagnostics equipment requiring stable component supply across extended product lifecycles.

Supply support for 25LC040AT-M/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 devices, and memory solutions, headquartered in Chandler, Arizona, with global design and manufacturing operations.

The 25LC040A family was designed specifically for reliable, low-power nonvolatile storage in resource-constrained embedded systems - emphasizing SPI simplicity, write safety, and long-term data integrity in harsh environments.

FAQ

What is the maximum SPI clock frequency supported by the 25LC040AT-M/SN?

The 25LC040AT-M/SN supports up to 10 MHz SPI clock frequency when VCC is 4.5 V to 5.5 V. At 2.5 V ≤ VCC < 4.5 V, the maximum clock drops to 5 MHz. These limits ensure reliable setup/hold timing for SI sampling and SO output validity across temperature and voltage ranges - critical for deterministic communication in real-time control loops. Always verify timing margins using the AC characteristics table in DS21827H.

Does the 25LC040AT-M/SN have built-in write protection beyond the WP pin?

Yes, the 25LC040AT-M/SN includes dual-layer write protection: hardware-level disable via the WP pin (pin 3), and software-configurable block protection via BP0/BP1 bits in the STATUS register. When WP is low, all writes are blocked regardless of WEL or BP settings. When WP is high, BP bits allow selective protection of none, upper 1/4, upper 1/2, or the full 512-byte array - providing flexible security for firmware, calibration, and user data partitions.

How does the HOLD pin function during an active SPI transaction on the 25LC040AT-M/SN?

The HOLD pin on the 25LC040AT-M/SN pauses an ongoing SPI sequence when pulled low while SCK is low; SI, SCK, and SO enter high-impedance states, and input transitions are ignored except for CS. To resume, HOLD must be raised while SCK remains low. This allows the host MCU to service urgent interrupts without losing bus synchronization - a key advantage over EEPROMs lacking HOLD, which would require full re-initialization after interruption.

What is the page size and write endurance specification for the 25LC040AT-M/SN?

The 25LC040AT-M/SN has a fixed page size of 16 bytes, meaning up to 16 consecutive bytes can be written in a single atomic page write operation - provided they reside within the same 16-byte-aligned boundary (e.g., addresses 00h–0Fh, 10h–1Fh). Its endurance is rated at 1,000,000 erase/write cycles per memory location, validated at 25°C and VCC = 5.5 V, ensuring longevity in applications like event logging or parameter tuning that involve frequent updates.

Is the 25LC040AT-M/SN pin-compatible with other Microchip 4 Kbit SPI EEPROMs like the 25AA040A?

Yes, the 25LC040AT-M/SN is pin-compatible and functionally identical to the 25AA040AT-I/SN in SOIC-8 (SN) packaging - sharing identical pinout, instruction set, timing, and register map. The primary difference is supply voltage range: 25LC040A requires 2.5–5.5 V, while 25AA040A operates down to 1.8 V. Both support HOLD, WP, and page write, making them drop-in replacements where voltage compliance matches the host system's rail.