Microchip Technology 25LC040T-I/SN

Overview

25LC040T-I/SN from Microchip Technology Inc. is a 4 Kbit (512 × 8) SPI-compatible serial EEPROM with 2.5–5.5 V supply range, 2 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 serial communication. It is used in embedded systems for nonvolatile storage of calibration data, configuration settings, and firmware parameters.

For engineers reviewing the 25LC040T-I/SN datasheet, 25LC040T-I/SN pinout, 25LC040T-I/SN application, or 25LC040T-I/SN equivalent, this page delivers verified electrical specs, validated SOIC-8 pin mapping, confirmed endurance (1M cycles), real-world timing constraints (e.g., 5 ms write cycle), and two field-tested alternative parts with documented functional differences.

Technical Context

The 25LC040T-I/SN 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 an 8-bit instruction register, STATUS register with WIP/WEL/BP bits, and page-based write logic that enforces 16-byte alignment across 32 pages.

It supports block write protection (none/¼/½/all array), self-timed erase/write cycles, and power-on reset of the write-enable latch. The HOLD pin suspends ongoing serial transfers without resetting the address pointer, enabling deterministic servicing of higher-priority interrupts while preserving EEPROM state.

Key Specifications

Pinout & Package

25LC040T-I/SN is packaged in an 8-pin SOIC (SN) with 150-mil body width and standard JEDEC MS-012 footprint. Pin 1 is marked by a beveled corner or dot; orientation follows standard SOIC conventions.

Key Features

Applications

Equivalent & Alternatives

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

Compared with 25LC040T-I/SN, 25AA040T-I/SN adds 1.8 V compatibility but sacrifices 2 MHz speed, while 25LC040A-I/SN retains full electrical and pin compatibility while delivering superior robustness and lifecycle support - making it the recommended upgrade path.

Availability

25LC040T-I/SN is available at Aetrix Electronics and suitable for industrial sensor calibration, medical device configuration, and automotive body control modules requiring stable component supply and long-term obsolescence management.

Supply support for 25LC040T-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 components, and memory solutions, headquartered in Chandler, Arizona, with global design and manufacturing operations.

The 25LC040T-I/SN belongs to Microchip's legacy SPI Serial EEPROM product line, designed specifically for cost-sensitive, space-constrained embedded systems requiring reliable nonvolatile storage with minimal external components.

FAQ

What is the maximum clock frequency supported by the 25LC040T-I/SN?

The 25LC040T-I/SN supports a maximum clock frequency of 2 MHz when VCC is between 2.5 V and 4.5 V. At VCC = 4.5–5.5 V, it supports up to 3 MHz, but the 25LC040 variant is specified only to 2 MHz per its Device Selection Table. This 2 MHz limit ensures reliable timing margins across the full industrial temperature range and supply voltage window of the 25LC040T-I/SN.

Does the 25LC040T-I/SN support page write operations?

Yes, the 25LC040T-I/SN supports 16-byte page write operations. Data written within the same 16-byte boundary (e.g., addresses 0x00–0x0F) can be loaded sequentially before initiating the internal write cycle. Exceeding the page boundary causes wraparound and potential data corruption - proper address alignment must be enforced in firmware to use page writes safely in the 25LC040T-I/SN.

How does the HOLD pin function during SPI communication with the 25LC040T-I/SN?

The HOLD pin on the 25LC040T-I/SN pauses ongoing SPI transfers without resetting the internal address pointer or command state. To activate HOLD, it must be pulled low while SCK is low; SO, SI, and SCK enter high-impedance states, and all inputs except CS are ignored. Resuming requires bringing HOLD high while SCK remains low. This behavior enables deterministic interrupt handling in time-critical applications using the 25LC040T-I/SN.

What write protection mechanisms are implemented in the 25LC040T-I/SN?

The 25LC040T-I/SN implements dual-layer write protection: (1) hardware via the WP pin (low = full write disable), and (2) software-configurable block protection via BP0/BP1 bits in the STATUS register (00 = no protection, 11 = full array protection). Both mechanisms operate simultaneously - if WP is low, software protection settings are overridden. This ensures fail-safe prevention of unintended writes in the 25LC040T-I/SN.

Is the 25LC040T-I/SN pin-compatible with other devices in the 25XX040 family?

Yes, the 25LC040T-I/SN is pin-compatible with 25AA040T-I/SN and 25C040T-I/SN in the same SOIC-8 (SN) package. All share identical pin functions, physical layout, and SPI instruction set. However, VCC ranges and maximum clock frequencies differ: 25AA040T-I/SN supports 1.8–5.5 V / 1 MHz, 25LC040T-I/SN supports 2.5–5.5 V / 2 MHz, and 25C040T-I/SN supports 4.5–5.5 V / 3 MHz - voltage and speed must be verified per application when substituting the 25LC040T-I/SN.