Microchip 24AA256T-I/SN 256K I2C Serial EEPROM: Features and Design Considerations

The Microchip 24AA256T-I/SN is a 256-Kbit (32-Kbyte) serial Electrically Erasable Programmable Read-Only Memory (EEPROM) that utilizes the ubiquitous I²C (Inter-Integrated Circuit) protocol. This device is engineered for reliability and performance in a wide array of applications, from consumer electronics to industrial systems. Its low-power consumption and high-noise immunity make it a preferred choice for designers seeking robust non-volatile memory solutions.

A key feature of this EEPROM is its 1.7V to 5.5V wide voltage range operation. This flexibility allows the same device to be seamlessly integrated into both modern low-voltage microcontrollers and legacy 5V systems, simplifying inventory and design across product families. Furthermore, it offers a maximum clock frequency of 1MHz (at 5.5V), enabling high-speed data transfers and efficient system throughput.

The 24AA256T is organized as 32,768 words of 8 bits each. It supports a page write buffer of 64 bytes, allowing for faster write cycles by writing multiple bytes in a single operation instead of individually. This significantly reduces the time the microcontroller spends on write routines. For data integrity, the device incorporates hardware write-protection via a WP (Write-Protect) pin. When asserted, this pin locks the entire memory array, preventing accidental writes and securing critical data.

Critical design considerations for implementing this EEPROM involve understanding the I²C bus limitations. Proper pull-up resistor selection on the SDA (Serial Data) and SCL (Serial Clock) lines is paramount; values typically range from 1kΩ to 10kΩ, depending on the bus capacitance and desired rise time. Designers must also account for the typical 5 ms write cycle time. The microcontroller firmware must include a polling routine or delay to ensure a subsequent write operation is not initiated before the current one is complete, preventing data corruption.

Another important consideration is the device addressing scheme. The 24AA256T has a 7-bit slave address, with three user-configurable address bits (A2, A1, A0). This allows up to eight identical devices to coexist on the same I²C bus, maximizing the available non-volatile memory capacity without requiring additional I/O pins from the host controller. Signal integrity is also crucial; for long board traces or noisy environments, ensuring clean SDA and SCL signals is necessary to avoid communication errors.

ICGOOODFIND: The Microchip 24AA256T-I/SN stands out as a highly versatile and reliable I²C EEPROM. Its combination of a wide voltage range, substantial storage capacity, hardware write-protection, and a page write mode makes it an excellent solution for countless embedded designs where dependable non-volatile data storage is required.

Keywords: I2C EEPROM, Non-volatile Memory, Low-power Operation, Page Write, Write-Protect.