Microchip Technology 24AA256UID-I/SN

Overview

24AA256UID-I/SN from Microchip Technology is a 256 Kbit I²C serial EEPROM with factory-programmed EUI-48™ and EUI-64™ node addresses, a unique 32-bit serial number, 1.7V–5.5V single-supply operation, and 64-byte page write buffer. It delivers industrial-grade reliability for secure device identification in networked embedded systems.

For engineers reviewing the 24AA256UID-I/SN datasheet, 24AA256UID-I/SN pinout, 24AA256UID-I/SN application, or 24AA256UID-I/SN equivalent, this page provides verified electrical specs, I²C timing compliance (100/400 kHz), permanent upper-array write protection, endurance (1M cycles), and real-world use context for UID-based authentication and asset tracking.

Technical Context

The 24AA256UID-I/SN implements a standard two-wire I²C slave interface with Schmitt-trigger inputs, slope-controlled outputs, and ACK polling support. Its memory map reserves the upper 1/8th (0x7000–0x7FFF) for permanently write-protected UID/EUI data, while the lower 229,376 bits (0x0000–0x6FFF) remain user-writable.

It supports cascaded bus configurations up to eight devices via A0–A2 address pins, uses internal address pointer auto-increment for sequential reads, and enforces strict page-boundary alignment for 64-byte page writes - crossing boundaries causes wraparound, not overflow.

Key Specifications

Pinout & Package

24AA256UID-I/SN is supplied in an 8-pin SOIC package (3.9mm × 4.9mm, 1.27mm pitch), RoHS-compliant, with gull-wing leads and matte tin plating. Pin 7 is NC (no connection); all other pins match standard I²C EEPROM pinout.

Key Features

Applications

Equivalent & Alternatives

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

Compared with 24AA256UID-I/SN, the 24AA256-I/SN omits factory UID data but matches all electrical and timing specs, while AT24CM01-UUM-MAA-T offers greater density and faster I²C but sacrifices IEEE node-address compatibility and UID structure consistency.

Availability

24AA256UID-I/SN is available at Aetrix Electronics and suitable for secure device authentication, network node identification, firmware version tracking, and calibration data storage requiring stable component supply across industrial, medical, and IoT product lifecycles.

Supply support for 24AA256UID-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, FPGA, and memory solutions, headquartered in Chandler, Arizona, with global design and manufacturing operations.

The 24AA256UID-I/SN belongs to Microchip's UID-family of serial EEPROMs, designed specifically to simplify secure device identity management in distributed systems without requiring external secure elements or complex provisioning infrastructure.

FAQ

What is the exact memory organization of the 24AA256UID-I/SN?

The 24AA256UID-I/SN contains 32,768 bytes (256 Kbit) organized as 32K × 8. The upper 1/8th (0x7000–0x7FFF = 4,096 bytes) is permanently write-protected and holds the 32-bit serial number (0x7FFC–0x7FFF), EUI-48™ (0x7F7A–0x7F7F), and EUI-64™ (0x7FB8–0x7FBF). The remaining 28,672 bytes (0x0000–0x6FFF) are fully user-writable. This layout is fixed and cannot be altered.

How does the 24AA256UID-I/SN handle I²C clock frequency scaling with supply voltage?

The 24AA256UID-I/SN automatically adapts its maximum I²C clock frequency based on VCC: it supports up to 400 kHz when VCC ≥ 2.5V, and degrades to 100 kHz when VCC < 2.5V. This behavior is hardwired and requires no software configuration - the device internally adjusts timing margins to maintain AC specification compliance across the full 1.7V–5.5V operating range.

Can the factory-programmed UID/EUI data in the 24AA256UID-I/SN be overwritten or erased?

No. The 32-bit serial number, EUI-48™, and EUI-64™ data stored in the upper 1/8th of the array (0x7000–0x7FFF) are permanently write-protected at the silicon level. Write attempts to this region are ignored; only read access is allowed. This protection is hardware-enforced and independent of software or external signals - it cannot be disabled or bypassed.

What is the purpose of the NC pin (Pin 7) on the 24AA256UID-I/SN SOIC package?

Pin 7 of the 24AA256UID-I/SN is designated NC (No Connection) - it is internally unconnected and must not be bonded or routed on the PCB. Leaving it floating is acceptable, but tying it to VSS is also permissible and may improve mechanical stability during reflow. Under no circumstances should it be connected to VCC, SDA, SCL, or any active signal, as it has no functional role and could cause unpredictable behavior if misused.

How does page write operation work in the 24AA256UID-I/SN, and what happens if a write crosses a 64-byte boundary?

The 24AA256UID-I/SN uses a 64-byte page buffer. During a page write, data is latched into the buffer and written to memory only after the master issues a Stop condition. If the master transmits more than 64 bytes before Stop, the address counter wraps around within the same physical page - overwriting earlier bytes in that page instead of advancing to the next page. Therefore, software must enforce strict 64-byte alignment to avoid unintended data corruption.