Microchip 25LC1024-I/MF 1-Mbit SPI Serial EEPROM: Features and Application Design Guide

The Microchip 25LC1024-I/MF is a high-density 1-Mbit Serial EEPROM device that utilizes the widely adopted SPI serial interface for efficient communication with a host microcontroller (MCU). This memory IC is designed for applications requiring reliable non-volatile data storage with low power consumption and a small form factor. Its combination of capacity, performance, and robustness makes it a compelling choice for a diverse range of modern electronic designs.

Key Features and Technical Specifications

At the core of the 25LC1024's appeal is its 1,048,576-bit memory array, organized as 128K x 8. This substantial storage capacity is packaged in an ultra-compact 8-pin DFN (2x3mm) package, making it ideal for space-constrained applications.

The device operates over a broad voltage range (1.8V to 5.5V), ensuring compatibility with both modern low-voltage microcontrollers and legacy 5V systems. It boasts impressive endurance, supporting over 1 million erase/write cycles per sector and offering data retention of over 200 years, guaranteeing long-term data integrity.

Communication is handled via a full-duplex SPI bus supporting clock speeds up to 10 MHz, enabling high-speed data transfer for time-sensitive operations. The interface supports all four SPI modes (0,0 and 1,1) for maximum flexibility. Furthermore, the 25LC1024 includes advanced hardware and software write-protection features. A dedicated Hold pin allows the MCU to pause a serial transfer without terminating it, which is critical in multi-master SPI environments.

Application Design Guide and Considerations

Integrating the 25LC1024 into a design is straightforward, but attention to several key areas will ensure optimal performance and reliability.

1. SPI Interface Configuration: The host MCU's SPI peripheral must be configured to match the EEPROM's settings: Clock Polarity (CPOL) and Phase (CPHA) set to mode 0,0 or 1,1, and a clock frequency not exceeding 10 MHz. The MCU should operate as the SPI Master, controlling the Chip Select (CS) line to initiate and terminate communication.

2. Hardware Connection: The typical wiring diagram is simple:

MCU SCLK → IC SCK (Serial Clock)

MCU MOSI → IC SI (Serial Input)

MCU MISO → IC SO (Serial Output)

MCU GPIO → IC CS (Chip Select)

MCU GPIO → IC HOLD (Optional, tie to VCC if unused)

MCU GPIO → IC WP (Write Protect, tie to VCC if unused)

Proper decoupling with a 0.1µF ceramic capacitor close to the VCC and VSS pins is essential for stable operation.

3. Memory Paging and Write Sequencing: The memory is organized in pages of 256 bytes. It is crucial to manage writes so that they do not cross page boundaries unintentionally. If a write sequence exceeds the end of a page, it will wrap around to the start of the same page, overwriting previously written data. Firmware must include checks to segment data into page-aligned writes.

4. Write Cycle Management: After issuing a Write Enable (WREN) command and any write command (e.g., BYTE WRITE or PAGE WRITE), the device becomes busy for the duration of the self-timed write cycle (typically 5 ms max). During this time, the device ignores all commands. The firmware must either wait for this period using a delay or, more efficiently, poll the Write Enable Latch (WEL) bit or the Write-In Progress (WIP) bit in the STATUS register to determine when the device is ready again.

5. Noise Immunity and PCB Layout: For applications in electrically noisy environments (e.g., industrial motor control), keep SPI trace lengths short and consider using series termination resistors on the clock and data lines to reduce ringing and overshoot. Ensuring a solid ground plane beneath the device significantly enhances signal integrity.

Typical Applications

This EEPROM is perfectly suited for storing system configuration data, calibration constants, and user settings in a vast array of products, including:

Industrial Automation and Sensor Modules

Automotive Electronics (non-critical data storage)

Medical Devices and Instrumentation

Smart Meters and IoT Edge Devices

Consumer Electronics and Telecommunications Equipment

ICGOOODFIND

The Microchip 25LC1024-I/MF stands out as a highly reliable and versatile non-volatile memory solution. Its large density, small physical size, and simple SPI interface make it an excellent choice for designers needing to add substantial, dependable data storage without complicating their design or consuming significant board space.

Keywords: SPI EEPROM, Non-volatile Memory, Microchip 25LC1024, Serial Interface, Data Storage