Microchip 24LC1026-I/SN 1024K I2C Serial EEPROM: Features and Application Design Guide
The Microchip 24LC1026-I/SN is a high-density, 1-Megabit (128K x 8) serial Electrically Erasable Programmable Read-Only Memory (EEPROM) that utilizes the ubiquitous I2C (Inter-Integrated Circuit) protocol for communication. This device is engineered for applications requiring non-volatile memory with reliable performance, low power consumption, and a simple two-wire interface. Its 128-byte page write buffer and hardware write-protection feature make it a versatile choice for a wide array of modern electronic systems.
Key Features and Specifications
The 24LC1026 boasts a set of features that distinguish it in the crowded memory market. Operating from 1.7V to 5.5V, it is exceptionally suited for both 5V and 3.3V systems, including battery-powered portable devices. Its low power consumption is highlighted by a standby current of just 1 µA (max) and an active read current of 1 mA (max) at 5.5V.
A critical feature of this EEPROM is its 1024K-bit capacity, organized as 128K words of 8 bits each. To manage this density within the I2C address space, the IC incorporates an address pin (A2) that acts as a most significant address bit, effectively enabling the memory to be viewed as two 512K bit blocks. This allows the device to respond to two unique I2C slave addresses (1010xxx0 and 1010xxx1), effectively doubling the addressable range.
The memory array supports a page write operation of 128 bytes, significantly speeding up the data writing process compared to byte-by-byte writes. It also features a 64-byte page on the 24AA1026/24LC1026 variant for certain operations. Endurance and data retention are robust, rated for 1,000,000 erase/write cycles and 200 years of data retention, respectively. The available SOIC (SN) package offers a compact footprint for space-constrained PCB designs.
Application Design Guide
Integrating the 24LC1026 into a design requires careful attention to the I2C bus and the device's specific operational characteristics.
1. Hardware Connection: The connection is straightforward. The Serial Data (SDA) and Serial Clock (SCL) lines require pull-up resistors (typically 4.7kΩ for 400 kHz, lower for higher speeds) to VCC. The address pin A2 must be tied to either VCC or GND to select the block and define the device's slave address. The Write-Protect (WP) pin is crucial for data integrity; when tied to VCC, the entire memory array is protected from write operations. For normal read/write operation, this pin must be connected to GND.
2. Communication Protocol: As a true I2C slave device, it supports standard (100 kHz), fast (400 kHz), and fast-mode plus (1 MHz) speeds. The data transfer protocol follows the standard I2C structure:
Start condition followed by a control byte. The control byte includes the 1010 device identifier, the block select bit (value of A2 pin), and a R/W bit.
This is followed by a 16-bit memory address (two bytes) specifying the location within the selected 512K block to read from or write to.
Data bytes are then transmitted (for write) or received (for read).
3. Writing Data: For write operations, after sending the address, the master transmits data. The internal write cycle time (tWC) is typically 5 ms. During this time, the device will not acknowledge its slave address, a condition known as busy polling. The master must wait for this period before attempting another communication.
4. Reading Data: Read operations are highly flexible. The most common method is a sequential read. The master initiates a write sequence to set the starting address and then sends a restart condition followed by a read command. The device will then output data sequentially, automatically incrementing the internal address pointer until the master issues a stop condition.
5. Noise and Signal Integrity: For long bus lines or electrically noisy environments, ensuring signal integrity is paramount. Proper PCB layout, with short traces and decoupling capacitors (0.1 µF) close to the VCC and GND pins, is essential. In extreme cases, using shielded cables or lowering pull-up resistor values may be necessary.
Typical Applications
This EEPROM is ideal for storing data that must be retained when power is removed. Common applications include:
Data logging in industrial sensors and meters.
Storing configuration parameters and calibration data in consumer electronics, medical devices, and networking equipment.
Smart meters for storing usage and tariff information.
Automotive systems for storing event data and user settings.
ICGOODFIND: The Microchip 24LC1026-I/SN stands out as a high-capacity, reliable, and easy-to-implement non-volatile memory solution. Its adherence to the standard I2C protocol, wide voltage range, and robust feature set, including hardware write-protection and high endurance, make it an excellent choice for designers across industries seeking to add substantial data storage capabilities to their systems.
Keywords: I2C EEPROM, Non-volatile Memory, Page Write, Hardware Write-Protection, Low-Power Design
