Microchip 24AA128-I/SN: A Comprehensive Overview of the 128K I2C Serial EEPROM
The Microchip 24AA128-I/SN is a high-performance 128Kbit I2C serial EEPROM memory chip designed for a wide range of applications requiring reliable non-volatile data storage. Organized as 16,384 words of 8 bits each, this device provides a robust solution for storing configuration parameters, calibration data, and other critical information in systems where power may be intermittently available.
Key Features and Electrical Characteristics
Housed in a compact 8-lead SOIC (SN) package, this EEPROM operates over an extensive voltage range of 1.7V to 5.5V, making it compatible with various logic levels and ideal for both 5V and 3.3V systems. Its low-power design is a significant advantage for battery-powered devices, featuring a standby current of just 1 μA (max.) and an active read current of 1 mA (max.) at 5.5V.
A critical performance metric for any memory is its endurance and data retention. The 24AA128 is specified for 1,000,000 erase/write cycles per byte, ensuring high reliability for frequently updated data. Furthermore, it guarantees data retention for over 200 years, safeguarding information for the lifetime of the end product.
The device supports a maximum clock frequency of 400 kHz for fast data transfer. It also includes hardware write-protection via the WC (Write Control) pin. When tied to VSS, the entire memory array is protected from inadvertent writes, which is crucial for data integrity.
I2C Interface and Addressing
As a true I2C-compatible device, it supports the two-wire serial interface protocol consisting of a Serial Data (SDA) line and a Serial Clock (SCL) line. The 24AA128 uses a 7-bit device address, with the four most significant bits fixed as `1010`. The following three bits (A2, A1, A0) are set by the user via the corresponding chip select pins, allowing up to eight individual devices (up to 1 Mbit total) to be connected on the same I2C bus, providing excellent design flexibility for expanding memory capacity.
Application Notes and Circuit Design Considerations
Successful implementation of the 24AA128 requires attention to several key design aspects. Pull-up resistors are mandatory on both the SDA and SCL lines to ensure proper logic levels; typical values range from 1 kΩ to 10 kΩ, depending on the bus capacitance and desired speed.
For systems operating in electrically noisy environments, decoupling capacitors (typically 0.1 μF to 1 μF) placed close to the VDD and VSS pins are essential to stabilize the power supply and prevent corruption during write cycles.
The chip features a page write buffer of 64 bytes. To maximize write efficiency and minimize total write time, developers should structure data writes to align with these page boundaries. Writing sequential bytes within a single page is significantly faster than writing random addresses across different pages.
Acknowledgment polling can be implemented in software after initiating a write cycle. By monitoring the ACK bit, the master device can determine when the internal write cycle is complete and the device is ready to receive new commands, simplifying software flow control.
ICGOOODFIND: The Microchip 24AA128-I/SN stands out as an exceptionally reliable and versatile serial EEPROM solution. Its combination of high density, low-power operation, robust endurance, and simple two-wire interface makes it an optimal choice for designers across consumer electronics, industrial systems, automotive modules, and Internet of Things (IoT) devices, providing a dependable foundation for non-volatile memory needs.
Keywords: I2C EEPROM, Non-volatile Memory, Serial Memory, Low-power Design, Data Storage.
