Microchip Technology 24AA256T-I/ST

Overview

24AA256T-I/ST from Microchip Technology is a 256-Kbit I²C-compatible serial EEPROM in an 8-lead SOIC package, operating from 1.7V to 5.5V with 400 kHz max clock frequency, 64-byte page write buffer, and hardware write-protection via WP pin. It delivers low-power operation (1 µA standby, 3 mA write) for embedded data logging and configuration storage in industrial control systems.

For engineers reviewing the 24AA256T-I/ST datasheet, 24AA256T-I/ST pinout, 24AA256T-I/ST application, or 24AA256T-I/ST equivalent, key selection criteria include voltage range compatibility (1.7–5.5V), I²C timing compliance at 400 kHz, page-write endurance (1M cycles), and SOIC-8 mechanical fit in space-constrained PCB layouts.

Technical Context

The 24AA256T-I/ST implements a two-wire I²C interface with Schmitt-trigger inputs on SDA/SCL for noise immunity and slope-controlled outputs to suppress ground bounce. Its internal address pointer supports sequential reads across the full 32K × 8 memory array, with automatic rollover from address 7FFFh to 0000h.

Write operations are self-timed and support both byte and page modes-up to 64 bytes per page write-with hardware write protection activated when WP = VCC. The device uses cascaded addressing (A0–A2 pins) to enable up to eight devices on one bus, though the SOIC package fully exposes all three address inputs for flexible multi-device topology.

Key Specifications

Pinout & Package

8-lead SOIC (Small Outline Integrated Circuit) package with standard 150-mil body width and 1.27 mm pitch; RoHS-compliant matte tin lead finish.

Key Features

Applications

Equivalent & Alternatives

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

Compared with 24LC256T-I/ST and AT24C256-10PU-2.7, the 24AA256T-I/ST uniquely supports 1.7V operation and AEC-Q100 industrial qualification while retaining full SOIC-8 pin compatibility-making it the only choice for ultra-low-power or automotive-adjacent embedded systems requiring guaranteed 200-year data retention.

Availability

24AA256T-I/ST is available at Aetrix Electronics and suitable for smart metering, industrial PLC configuration, and medical device calibration requiring stable component supply across extended product lifecycles.

Supply support for 24AA256T-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, and Flash-IP solutions, serving industrial, automotive, and consumer markets with vertically integrated silicon and development tools.

The 24AA256T-I/ST belongs to Microchip's 24XX256 family of I²C EEPROMs, designed specifically for reliable, low-power nonvolatile data storage in space- and power-constrained embedded systems requiring long-term data integrity.

FAQ

What is the maximum I²C clock frequency supported by the 24AA256T-I/ST?

The 24AA256T-I/ST supports up to 400 kHz I²C clock frequency across its full 1.7V–5.5V supply range. At VCC < 2.5V, the maximum clock rate remains 400 kHz-unlike the 24LC256 variant, which drops to 100 kHz below 2.5V. This ensures consistent high-speed communication in battery-powered or low-voltage microcontroller systems. The 24AA256T-I/ST datasheet confirms this in Table 1-2, Parameter 1 (FCLK).

Does the 24AA256T-I/ST support hardware write protection, and how is it implemented?

Yes, the 24AA256T-I/ST implements hardware write protection via the WP (Write-Protect) pin. When WP is tied to VCC, all write operations-including byte and page writes-are inhibited, while read operations remain fully functional. The WP state is sampled at the STOP condition of each write command, making protection effective immediately without software configuration. This feature is documented in Section 6.3 and Pin Function Table 2-1 of the 24AA256T-I/ST datasheet.

What package type is used for the 24AA256T-I/ST, and what are its key mechanical features?

The 24AA256T-I/ST uses an 8-lead SOIC (Small Outline Integrated Circuit) package, designated "ST" in the part number. It has a 150-mil body width, 1.27 mm lead pitch, and RoHS-compliant matte tin (Sn) plating. The package marking includes "24AA256T" followed by temperature code "I" and date code, as shown in Figure 9-1 of the 24AA256T-I/ST datasheet. This SOIC-8 footprint ensures broad compatibility with legacy and new PCB designs.

How many devices can be connected on the same I²C bus using the 24AA256T-I/ST?

Up to eight 24AA256T-I/ST devices can be connected on the same I²C bus using the A0, A1, and A2 address input pins. Each pin configures one bit of the 3-bit chip address (1010 A2 A1 A0 R/W), enabling unique addressing across the bus. All three pins are fully functional in the SOIC package, unlike MSOP or SOT-23 variants where some address pins are NC. This capability is detailed in Sections 2.1 and 5.0 of the 24AA256T-I/ST datasheet.

What is the page write buffer size and maximum write cycle time for the 24AA256T-I/ST?

The 24AA256T-I/ST features a 64-byte page write buffer and a maximum write cycle time of 5 ms for both byte and page writes. During page write, up to 64 bytes are latched internally and written in a single self-timed operation-reducing total programming time versus sequential byte writes. This specification is confirmed in the Features list and Table 1-2 (Parameter 17, TWC) of the 24AA256T-I/ST datasheet.