Microchip 24LC1025-E/SN 1024K I2C Serial EEPROM: Features and Application Design Guide
The Microchip 24LC1025-E/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 reliable non-volatile data storage with minimal pin count and power consumption. Its combination of capacity, ease of use, and robustness makes it a cornerstone component in countless electronic designs.
Key Features and Specifications
The 24LC1025-E/SN stands out due to a set of powerful features tailored for modern electronics:
High-Density Memory: Organized as 131,072 words of 8 bits each, it provides ample space for storing data tables, system parameters, calibration constants, and event logs.
I2C Serial Interface: Supports the two-wire I2C bus protocol (SDA and SCL), significantly reducing the number of I/O pins required from the host microcontroller, simplifying board layout.
Wide Voltage Operation: It operates across a broad voltage range of 1.7V to 5.5V, making it compatible with various logic levels, from low-power microcontrollers to legacy 5V systems.
Page Write Capability: Features a 128-byte page write buffer, allowing for faster data writes by sending up to 128 bytes in a single write cycle.
Hardware Write-Protect: The WP (Write-Protect) pin allows the user to enable a hardware-based lock on the entire memory array, preventing accidental data corruption.
High Reliability: Endured for 1,000,000 erase/write cycles per byte and offers >200 years of data retention.
Extended Temperature Range: The ‘E’ suffix denotes its operation over the industrial temperature range (-40°C to +85°C), ensuring performance in harsh environments.
Packaging: The SN package is an 8-lead SOIC, which is a common and easy-to-assemble surface-mount package.
Application Design Guide
Successfully integrating the 24LC1025 into a design requires attention to several key areas:
1. I2C Bus Configuration:
The device supports a maximum clock frequency of 400 kHz (Fast-mode). Two address pins (A1, A2) allow up to four 24LC1025 devices to be connected on the same bus, providing a total of 4Mb of memory. The 24LC1025 has a 2-bit device address code (1010), followed by the pin-select bits (A2, A1) and a block select bit that chooses between the lower or upper 64K of the memory space.
2. Pull-up Resistor Selection:
The I2C bus lines (SDA and SCL) are open-drain and require external pull-up resistors. The value of these resistors is a trade-off between bus speed and power consumption. Typical values range from 2.2 kΩ for fast modes (400 kHz) at 5V to 10 kΩ for standard mode (100 kHz) or lower-voltage systems. The total bus capacitance must be considered to ensure signal integrity.
3. Write Protection Strategy:
Tie the WP pin to VSS or control it via a microcontroller GPIO. Driving WP high (VCC) protects the entire memory array. This is critical for storing immutable calibration data or protecting firmware from being overwritten during a system fault.
4. Power Management and Sequencing:
Ensure power supply decoupling with a 100 nF ceramic capacitor placed as close as possible to the VCC and VSS pins of the IC. This mitigates noise and ensures stable operation. Be mindful of the device's power-down requirements to prevent incomplete write cycles during a brown-out or reset condition.
5. Handling Page Writes:
To maximize write efficiency, always structure data writes in full 128-byte pages when possible. This minimizes the number of write cycles and speeds up data storage. Remember that crossing a 128-byte page boundary within a single write command will cause the address pointer to wrap around to the start of the same page, leading to data corruption.
6. Acknowledge Polling:
After initiating a write cycle, the device will not respond until the cycle is complete (typically 5 ms max). The host can use acknowledge polling: it sends a start condition and the device address. If the device is busy, it will not generate an ACK. Once it does ACK, the write cycle is finished, and the host can proceed.
Common Applications
This EEPROM is ideal for use in:
Data logging systems in industrial and automotive environments.
Smart meters for storing cumulative consumption data.
Medical devices for retaining patient data and device settings.
Networking equipment for storing configuration parameters.
Consumer electronics, including smart TVs and set-top boxes.
ICGOOODFIND
The Microchip 24LC1025-E/SN is an exceptionally versatile and reliable serial EEPROM solution. Its high density, simple two-wire interface, and robust feature set make it an optimal choice for designers seeking to add substantial non-volatile memory without complicating their design. Careful attention to bus layout, pull-up resistors, and write-cycle management is key to unlocking its full potential in any application.
Keywords:
I2C EEPROM
Non-volatile Memory
Microchip 24LC1025
Page Write
Hardware Write-Protect
