Microchip Technology 24AA256-I/ST

Overview

24AA256-I/ST from Microchip Technology is a 256-Kbit I²C serial EEPROM with 32K × 8 organization, operating from 1.7V to 5.5V, supporting up to 400 kHz clock frequency at industrial temperature (−40°C to +85°C), and featuring hardware write-protection via the WP pin. It delivers 64-byte page write buffer, 1 µA standby current, and >1 million erase/write cycles - deployed in embedded systems for configuration storage, calibration data retention, and firmware parameter backup.

For engineers reviewing the 24AA256-I/ST datasheet, 24AA256-I/ST pinout, 24AA256-I/ST application, or 24AA256-I/ST equivalent, key selection criteria include low-voltage operation down to 1.7V, I²C bus compatibility with Schmitt-trigger inputs and slope-controlled outputs, cascading support for up to eight devices on one bus, and factory-programmable options for secure boot or device identity storage.

Technical Context

The 24AA256-I/ST implements a two-wire I²C interface with standard and fast-mode timing compliance (100 kHz / 400 kHz), using open-drain SDA/SCL with external pull-ups. Its internal address pointer enables sequential reads across the full 256-Kbit memory space, while hardware write-protection isolates the entire array when WP = VCC.

It integrates a 64-byte page write buffer with self-timed erase/write cycles (≤5 ms), Schmitt-trigger inputs for noise immunity, and output slope control to suppress ground bounce. Addressing uses three configurable chip-select pins (A0–A2) to support up to eight devices on a shared bus - though A0 and A1 are unconnected in the ST (SOIC) package per datasheet Table 2-1.

Key Specifications

Pinout & Package

24AA256-I/ST is supplied in an 8-lead SOIC (Small Outline Integrated Circuit) package, designated "ST" in Microchip's ordering nomenclature. Pin 1 is marked with a beveled corner or dot; the package is RoHS-compliant and rated for industrial temperature range (−40°C to +85°C).

Key Features

Applications

Equivalent & Alternatives

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

Compared with 24LC256-I/ST, the 24AA256-I/ST enables 1.7V operation and 10× higher endurance, making it superior for battery-powered or safety-critical applications; versus AT24C256, it trades 1 MHz speed for robustness in harsh environments and longer field life.

Availability

24AA256-I/ST is available at Aetrix Electronics and suitable for industrial sensor calibration, medical device configuration, smart energy meter firmware, and automotive body control modules requiring stable component supply, long-term data integrity, and automotive-grade reliability.

Supply support for 24AA256-I/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 microcontroller, analog, FPGA, and memory solutions, headquartered in Chandler, Arizona, with global design and manufacturing operations.

The 24AA256 belongs to Microchip's serial EEPROM product line, engineered for ultra-low-power, high-reliability nonvolatile storage in resource-constrained embedded systems across industrial, medical, and automotive markets.

FAQ

What is the minimum supply voltage required for reliable operation of the 24AA256-I/ST?

The 24AA256-I/ST operates reliably down to 1.7V across its full industrial temperature range (−40°C to +85°C). This enables direct integration with 1.8V microcontrollers and extends battery runtime in portable equipment - unlike the 24LC256 variant, which requires ≥2.5V. The 24AA256-I/ST maintains full I²C functionality, including 400 kHz clock support and page write capability, at 1.7V.

How does the WP pin function on the 24AA256-I/ST, and what happens if it is left floating?

The WP (Write-Protect) pin on the 24AA256-I/ST is a logic-level input: tied to VCC, it disables all write operations (including page and byte writes) while permitting reads; tied to VSS, writes are enabled. Per datasheet Section 2.4, WP must be actively driven to VSS or VCC - leaving it floating violates absolute maximum ratings and may cause unpredictable behavior or partial write inhibition. A pull-down resistor (e.g., 10 kΩ to VSS) is recommended for default-enable configurations.

Can multiple 24AA256-I/ST devices share the same I²C bus, and how many are supported?

Yes, up to eight 24AA256-I/ST devices can share one I²C bus using hardware address lines A2, A1, and A0. Each device is assigned a unique 3-bit chip address (1010 A2 A1 A0), allowing distinct responses to the same I²C master. However, in the SOIC-8 "ST" package, A0 and A1 are unconnected (NC) per datasheet Table 2-1 - only A2 is functional, limiting cascading to two devices (A2 = 0 or 1) on the same bus for this specific variant.

What is the maximum write time for a full 64-byte page on the 24AA256-I/ST?

The 24AA256-I/ST guarantees a maximum write cycle time of 5 ms for both single-byte and full 64-byte page writes. This self-timed duration includes internal charge-pump programming and verify steps - no external delay is needed. During this period, the device does not acknowledge I²C commands (ACK polling is used to detect completion), ensuring deterministic timing for real-time systems managing multiple EEPROMs.

Is the 24AA256-I/ST qualified for automotive applications, and what is its temperature rating?

The 24AA256-I/ST is rated for industrial temperature range (−40°C to +85°C), indicated by the "I" suffix. It is not AEC-Q100 qualified - that certification applies only to the 24AA256-E/ST (extended temp) and automotive-specific variants like 24AA256T-I/MNY. For automotive body control or infotainment modules requiring AEC-Q100 Grade 2, the 24AA256-I/ST may be used only if system-level validation confirms robustness within the vehicle's thermal envelope and EMC profile.