Microchip Technology 24AA256-E/ST

Overview

24AA256-E/ST from Microchip Technology is a 256-Kbit I²C-compatible serial EEPROM with 32K × 8 organization, operating from 1.7V to 5.5V, supporting up to 400 kHz clock frequency, and rated for industrial temperature range (–40°C to +85°C). It features 64-byte page write buffer, hardware write-protection via WP pin, and Schmitt-trigger inputs for noise immunity - deployed in embedded system configuration storage and sensor calibration data retention.

For engineers reviewing the 24AA256-E/ST datasheet, 24AA256-E/ST pinout, 24AA256-E/ST application, or 24AA256-E/ST equivalent, key selection criteria include low-voltage operation down to 1.7V, 1 µA standby current, I²C bus compatibility across multiple voltage levels, cascading support for up to eight devices on one bus, and factory-programmable options for pre-loaded firmware or calibration tables.

Technical Context

The 24AA256-E/ST implements a two-wire I²C interface with open-drain SDA/SCL lines requiring external pull-ups, and uses internal address pointer logic to support current-address, random, and sequential read modes. Its memory array is organized as 32,768 bytes with automatic page boundary handling during writes.

Write operations are self-timed and internally managed: byte writes complete in ≤5 ms, and page writes (up to 64 bytes) also require ≤5 ms. The device samples the WP pin at the Stop bit to enable or disable write cycles, and supports acknowledge polling to detect write completion without fixed delay timing.

Key Specifications

Pinout & Package

24AA256-E/ST is supplied in an 8-lead SOIC package (3.90 mm width) with standard JEDEC MS-012AC footprint. Pin 1 is marked with a beveled corner or dot; pin numbering follows counter-clockwise convention starting from top-left when notch faces upward.

Key Features

Applications

Equivalent & Alternatives

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

Compared with 24LC256-I/ST and AT24C256-10PU-2.7, the 24AA256-E/ST uniquely supports 1.7V operation and offers 10× higher endurance - making it the preferred choice for battery-powered, low-voltage, or high-update-frequency applications where long-term reliability is critical.

Availability

24AA256-E/ST is available at Aetrix Electronics and suitable for industrial sensor nodes, medical device calibration storage, and smart energy metering requiring stable component supply, long-term lifecycle support, and RoHS-compliant packaging.

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

The 24AA256-E/ST belongs to Microchip's 24XX256 family of I²C serial EEPROMs, engineered for ultra-low-power, wide-voltage-range data retention in embedded systems where reliability, longevity, and bus simplicity are essential.

FAQ

What is the minimum operating voltage for the 24AA256-E/ST?

The 24AA256-E/ST operates down to 1.7V, enabling direct integration with 1.8V logic families and battery-powered systems experiencing voltage sag. This specification is confirmed in the Device Selection Table and Electrical Characteristics section of the DS20001203Y datasheet, where VCC range is explicitly listed as 1.7V–5.5V for the 24AA256 variant.

Does the 24AA256-E/ST support page write operations, and what is the buffer size?

Yes, the 24AA256-E/ST supports page write operations with a 64-byte page write buffer. This allows up to 64 bytes to be loaded into the internal latch before initiating a single self-timed write cycle, significantly reducing I²C transaction overhead compared to byte-wise writes. The 64-byte limit and ≤5 ms write time are specified in the Features and AC Characteristics sections of the datasheet.

How does hardware write-protection work on the 24AA256-E/ST?

The WP (Write-Protect) pin on the 24AA256-E/ST provides hardware-level write inhibition: when tied to VCC, all write operations (byte and page) are blocked while read access remains fully functional. The pin is sampled at the Stop bit of each write command, and its state is latched for that cycle. This behavior is documented in Section 6.3 "Write Protection" and Pin Function Table of the DS20001203Y datasheet.

Can multiple 24AA256-E/ST devices share the same I²C bus?

Yes, up to eight 24AA256-E/ST devices can be cascaded on a single I²C bus using the A0, A1, and A2 address inputs to configure unique 3-bit chip addresses. Each device responds only to its assigned address, enabling scalable memory expansion up to 2 Mbit. This capability is detailed in the Device Addressing section (Section 5.0) and Device Selection Table of the datasheet.

What is the data retention period and endurance rating for the 24AA256-E/ST?

The 24AA256-E/ST guarantees >200 years of data retention at +25°C and 1,000,000 erase/write cycles per page. These values are measured under specified conditions (25°C, 5.5V, page mode) and reflect actual characterization results, not extrapolated projections. Both specifications appear in the Features list and TABLE 1-2 (AC Characteristics) of the DS20001203Y datasheet.