25LC1024-I

The 25LC1024-I is a 1 Mbit (128 K x 8-bit) SPI serial EEPROM from Microchip Technology, representing the highest-density member of the 25-series SPI EEPROM family. The -I suffix denotes industrial temperature range (-40°C to +85°C), and the LC designation indicates 2.5 V minimum operating voltage.

Organized as 131,072 bytes (128 KB), the 25LC1024 provides substantial non-volatile storage capacity for applications such as high-end data logging, firmware storage, calibration parameters, and configuration data. The SPI interface supports clock frequencies up to 10 MHz, offering significantly higher throughput than I2C-based alternatives for large data transfers.

Both SPI Mode 0 (CPOL=0, CPHA=0) and Mode 3 (CPOL=1, CPHA=1) are supported, ensuring compatibility with virtually all microcontroller SPI peripherals. The 256-byte page write buffer allows efficient block programming, with up to 256 contiguous bytes programmable in a single 5 ms self-timed write cycle. Sequential read allows the entire memory array to be read continuously after a single address setup, maximizing data throughput.

Write protection is comprehensive: a hardware Write-Protect (WP) pin combined with software-configurable block protection bits (BP0, BP1, BP2) in the status register allows protecting none, one-quarter, one-half, or the entire memory array. This flexible protection scheme enables partitioning of the memory into protected and unprotected regions. A /HOLD pin allows the master to pause a serial transfer without resetting the communication sequence, useful when a higher-priority device needs to use the SPI bus.

The device features built-in power-on reset and brown-out protection to prevent corrupt writes during power supply transitions. With over 1 million erase/write cycles per byte and greater than 200-year data retention, the 25LC1024 offers exceptional reliability for long-lifecycle products. It is available in multiple package options including PDIP, SOIC, TSSOP, and DFN to suit various board design requirements.

The 25LC1024 is a 1 Mbit SPI EEPROM with the same core architecture as other 25-series devices:

1. Memory Array: 131,072 bytes (1 Mbit) of EEPROM memory organized as 128K x 8 bits. 512 pages of 256 bytes each. Data is stored in floating-gate CMOS EEPROM cells with Fowler-Nordheim tunneling for program and erase operations. Non-volatile data retention exceeds 200 years.

2. SPI Interface: 4-wire SPI interface (/CS, SCK, SI, SO). Supports Mode 0 (0,0) and Mode 3 (1,1). Max clock frequency: 10 MHz at 5V supply.

3. Instruction Set: READ, WRITE, WREN (Write Enable), WRDI (Write Disable), RDSR (Read Status Register), WRSR (Write Status Register), plus PE (Page Erase) and CE (Chip Erase) on this larger device.

4. Status Register: 8-bit register containing WIP (Write-In-Progress), WEL (Write Enable Latch), BP0/BP1/BP2 (Block Protection bits), and WPEN (Write Protect Enable). Block protection can cover none, 1/4, 1/2, or the entire array.

5. Write Operation: Byte write or page write (up to 256 bytes). Self-timed write cycle with auto-erase. Max 5 ms, typical 3 ms. Acknowledge via WIP bit polling.

6. Read Operation: Random read after address setup, or sequential read where address auto-increments. Entire 128 KB array can be read in one continuous operation.

7. Power: 3 mA active read current (10 MHz, 5.5V), 5 µA standby current. Built-in power-on reset and brown-out detection for write protection at low voltage.

8-Pin Pinout (PDIP/SOIC/TSSOP – top view):

   /CS  1-+---+-8  Vcc
    SO  2-|   |-7  /HOLD
   /WP  3-|   |-6  SCK
   GND  4-+---+-5  SI

Package options: -I/P = 8-pin PDIP (through-hole), -I/SN = SOIC-8 (150mil), -I/ST = TSSOP-8, -I/MF = DFN-8 (2x3mm). Standard 25-series 8-pin pinout. Industrial temperature grade: -40°C to +85°C ambient. RoHS compliant, lead-free.

• High-End Industrial Data Logging: Industrial data loggers and process recorders storing high-frequency sampled data with timestamps. The 128 KB capacity and 10 MHz SPI interface enable rapid data recording for extended periods. Page writes (256 bytes) maximize write throughput for bulk data capture.
• Automotive Electronics and Telematics: Automotive ECUs, black-box event data recorders, and telematics units storing trip history, fault code logs, and driver behavior data. High endurance (1M cycles) supports frequent writes, and automotive AEC-Q100 qualified versions are available for under-hood applications.
• High-Throughput Configuration and Data Storage: Applications requiring faster data transfer than I2C EEPROMs can provide, such as large configuration tables, image parameters, and user profile storage. The 10 MHz SPI clock is roughly 25x faster than I2C Fast Mode.
• Firmware Backup and Boot Memory: Secondary firmware storage, boot parameter storage, and FPGA configuration backup where large non-volatile capacity is needed but SPI flash is overkill. 128 KB fits most MCU bootloader and parameter storage needs.
• Medical Device Data and Event Logging: Patient monitors, diagnostic equipment, and therapeutic devices storing treatment logs, patient data, and device usage history. High data integrity and >200 year retention ensure critical medical data is reliably preserved.
• Smart Meters and Energy Management: Advanced smart meters storing interval data, TOU tariff tables, load profile records, and network parameters. 128 KB capacity stores months of interval data, and block protection prevents tampering with critical calibration data.
• Networking Equipment Parameters: Enterprise routers, switches, and gateways storing configuration data, port statistics, firmware images, and security keys. Multiple devices can share the SPI bus using individual /CS signals, with /HOLD for transaction pausing.
• Sensor Calibration and Parameter Tables: Multi-channel smart sensor systems and industrial transmitters storing comprehensive calibration tables, temperature compensation coefficients, and sensor identification data. Block write protection locks factory calibration, ensuring long-term measurement accuracy.