Microchip Technology 24LC256-E/ST

Overview

24LC256-E/ST from Microchip Technology is a 256-Kbit I²C serial EEPROM with 32K × 8 organization, operating from 2.5V to 5.5V, supporting up to 400 kHz clock frequency, and rated for industrial temperature range (–40°C to +85°C). It features hardware write-protection via the WP pin, 64-byte page write buffer, and Schmitt-trigger inputs for noise immunity - deployed in embedded system configuration storage, sensor calibration data retention, and power-fail-safe parameter logging.

For engineers reviewing the 24LC256-E/ST datasheet, 24LC256-E/ST pinout, 24LC256-E/ST application, or 24LC256-E/ST equivalent, key selection criteria include its 2.5V minimum VCC, 400 kHz I²C speed at full voltage, 1 µA standby current, page write time ≤5 ms, and SOIC-8 package compatibility with legacy board layouts.

Technical Context

The 24LC256-E/ST implements a two-wire I²C interface with open-drain SDA/SCL pins requiring external pull-ups, supports cascading up to eight devices via A0–A2 address inputs, and uses internal address pointer logic for sequential reads across the full 0000h–7FFFh memory space. Its EEPROM array employs self-timed erase/write cycles with automatic page boundary handling.

It integrates Schmitt-trigger inputs on SDA and SCL for robust noise suppression, slope-controlled outputs to minimize ground bounce, and hardware write-protection that disables all writes when WP = VCC - independent of I²C command execution. The device does not generate ACK during internal write cycles, enabling reliable acknowledge polling for timing-critical firmware.

Key Specifications

Pinout & Package

24LC256-E/ST is supplied in an 8-lead SOIC (Small Outline Integrated Circuit) package with standard 150-mil body width and 1.27 mm pitch. Pin 1 is marked with a beveled corner or dot; orientation follows JEDEC MS-012.

Key Features

Applications

Equivalent & Alternatives

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

Compared with 24AA256-I/ST and AT24C256-10PU-2.7, the 24LC256-E/ST delivers optimal trade-off of industrial temperature rating, 400 kHz I²C speed, Schmitt-trigger noise immunity, and 2.5V operational floor - making it preferred for embedded control systems demanding reliability and responsiveness.

Availability

24LC256-E/ST is available at Aetrix Electronics and suitable for industrial sensor calibration storage, medical device configuration backup, and automotive body control module settings requiring stable component supply and long-term lifecycle support.

Supply support for 24LC256-E/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 components, and memory solutions, headquartered in Chandler, Arizona, with global design and manufacturing operations.

The 24LC256 belongs to Microchip's 24XX256 family of I²C-compatible serial EEPROMs, engineered for low-power, high-reliability nonvolatile data storage in space-constrained embedded systems.

FAQ

What is the minimum supply voltage required for reliable operation of the 24LC256-E/ST?

The 24LC256-E/ST requires a minimum VCC of 2.5V for guaranteed functionality across its full specification - including 400 kHz I²C communication, page write, and read operations. Operation below 2.5V is not characterized and may result in incomplete writes or communication failures. This distinguishes it from the 24AA256 variant, which supports down to 1.7V.

Does the 24LC256-E/ST support multi-device addressing on the same I²C bus?

Yes, the 24LC256-E/ST supports multi-device addressing via three hardware-configurable chip-select pins (A0, A1, A2), allowing up to eight devices on a single I²C bus. Each device responds only to its unique 7-bit address (1010xxx), where xxx corresponds to the binary state of A2–A0. All pins must be hardwired to VSS or VCC - floating connections are invalid.

How does hardware write-protection work on the 24LC256-E/ST?

Hardware write-protection on the 24LC256-E/ST is controlled by the WP pin: when tied to VCC, all write operations (byte, page, and erase) are blocked while read operations remain fully functional. The WP state is sampled at the STOP condition of each write command - toggling WP mid-cycle has no effect. This provides deterministic, silicon-level protection against accidental or malicious writes.

What is the maximum page write size supported by the 24LC256-E/ST?

The 24LC256-E/ST supports a maximum page write size of 64 bytes. Writes crossing physical page boundaries (every 64-byte aligned block from 0000h, 0040h, 0080h, etc.) wrap around within the current page instead of advancing to the next. To avoid data corruption, firmware must ensure page write commands do not span these boundaries - requiring explicit address alignment checks before initiating multi-byte writes.

Can the 24LC256-E/ST be used in automotive applications?

The 24LC256-E/ST is rated for industrial temperature range (–40°C to +85°C) and meets AEC-Q100 stress test requirements, making it suitable for under-dash automotive applications such as body control modules and infotainment subsystems. However, it is not qualified for under-hood (Grade 1, –40°C to +125°C) use - for that, the 24LC256-E/MNY (extended temp) variant is specified.