Microchip Technology 24LC256-E/SM

Overview

24LC256-E/SM 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 systems requiring nonvolatile parameter storage and firmware configuration retention.

For engineers reviewing the 24LC256-E/SM datasheet, 24LC256-E/SM pinout, 24LC256-E/SM application, or 24LC256-E/SM equivalent, key selection criteria include VCC min/max compliance, I²C timing at target bus speed, WP pin behavior during power-up, endurance (1M cycles), and package-specific address pin availability (A0/A1 unconnected in MSOP).

Technical Context

The 24LC256-E/SM implements a two-wire I²C-compatible interface with open-drain SDA/SCL pins requiring external pull-ups. Its internal address counter supports current-address, random, and sequential reads across the full 0000h–7FFFh memory space. Device addressing uses a fixed 4-bit control code (1010b) plus three user-configurable chip-select bits (A2, A1, A0), though A0 and A1 are not connected in the SOIJ-8 (SM) package.

Write operations are self-timed: byte writes complete in ≤5 ms; page writes (up to 64 bytes within one physical page boundary) also require ≤5 ms. Acknowledge polling is supported to detect write completion without fixed delays. The WP pin is sampled at the Stop bit of each write command - high disables all writes, low enables them.

Key Specifications

Pinout & Package

24LC256-E/SM is supplied in an 8-lead SOIJ (Small Outline J-bend) package, designated "SM" per Microchip's packaging nomenclature. This package has J-shaped leads, 3.9 mm body width, and exposes no thermal pad. Pins A0 and A1 are functional and connected (unlike MSOP), supporting full 3-bit device addressing.

Key Features

Applications

Equivalent & Alternatives

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

Compared with 24AA256-I/SN and AT24C256-10PU-2.7, the 24LC256-E/SM delivers optimal balance of industrial temperature rating, hardware write protection reliability, and proven noise immunity - making it preferred for mission-critical embedded storage where voltage stability and bus integrity are guaranteed.

Availability

24LC256-E/SM is available at Aetrix Electronics and suitable for industrial sensor calibration, medical device configuration, automotive body control modules, and smart energy meter firmware patching requiring stable component supply across extended production lifecycles.

Supply support for 24LC256-E/SM 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 legacy serial EEPROM product line, engineered for reliable, low-power, I²C-based nonvolatile storage in industrial, automotive, and medical applications where data integrity and long-term retention are essential.

FAQ

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

The 24LC256-E/SM requires a minimum VCC of 2.5V for guaranteed operation across its full specification - including 400 kHz I²C timing, write functionality, and data retention. Operation below 2.5V is not supported, unlike the 24AA256 variant which operates down to 1.7V. This makes the 24LC256-E/SM ideal for stable 3.3V or 5V systems where voltage regulation is well-controlled.

Does the 24LC256-E/SM support page writes across memory boundaries?

No, the 24LC256-E/SM does not support page writes across physical page boundaries. Its 64-byte page buffer wraps around within the same 64-byte page (e.g., writing 65 bytes starting at address 0x003F will overwrite byte 0x0000 instead of proceeding to 0x0040). Application firmware must explicitly manage page alignment - the 24LC256-E/SM enforces this at the hardware level to prevent unintended corruption.

How does the WP pin function during power-up sequences in the 24LC256-E/SM?

The WP pin state is sampled only at the Stop condition of each write command - not continuously. During power-up, if WP is held high, all subsequent write attempts will be ignored (though the device still acknowledges the command). To ensure safe default behavior, tie WP to VSS through a pull-down resistor unless intentional write protection is required during normal operation.

Can multiple 24LC256-E/SM devices share the same I²C bus?

Yes, up to eight 24LC256-E/SM devices can share one I²C bus using hardware address pins A2, A1, and A0. Each device must have a unique combination of these pins tied to VCC or VSS to generate distinct 7-bit client addresses (1010+A2A1A0). The SOIJ-8 (SM) package fully supports all three address pins - unlike MSOP variants where A0/A1 are NC.

What is the typical write cycle time for a single byte using the 24LC256-E/SM?

The 24LC256-E/SM guarantees a maximum write cycle time of 5 ms for both byte and page writes. This is a self-timed internal operation - the device releases the I²C bus after the Stop condition and does not respond to further commands until the cycle completes. Host systems should use acknowledge polling (repeated START + write address) rather than fixed delays to detect completion efficiently.