24LC1025-I

The 24LC1025-I is a 1 Mbit (128 K x 8-bit) I2C serial EEPROM from Microchip Technology, offering high-density non-volatile memory with an industry-standard 2-wire interface. 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 24LC1025 provides a large non-volatile storage solution for parameter storage, configuration data, calibration tables, event logs, and firmware backup. The device features both byte write and page write operations. The 128-byte page write buffer allows writing up to 128 contiguous bytes in a single write cycle (5 ms max), dramatically improving write throughput compared to byte-by-byte programming.

The I2C interface supports Standard Mode (100 kHz) and Fast Mode (400 kHz) operation, ensuring compatibility with virtually all microcontroller I2C peripherals. Schmitt trigger inputs on SCL and SDA provide excellent noise immunity in electrically noisy industrial environments. Output slope control helps minimize electromagnetic interference (EMI) and ground bounce.

Device addressing is provided by two external address pins (A0, A1), with A2 internally tied to Vcc. This allows cascading up to four 24LC1025 devices on the same I2C bus, for a total of up to 4 Mbits of system EEPROM memory. The internal A2-to-Vcc connection means the device always responds to addresses where the A2 bit is 1.

A hardware Write-Protect (WP) pin provides full-array write protection when pulled high, preventing accidental writes to the entire memory array. This is especially useful for protecting factory calibration data and other critical parameters from corruption due to software bugs or electrical transients.

The device features exceptional reliability with more than 1 million erase/write cycles per byte and greater than 200-year data retention. The self-timed write cycle includes automatic erase-before-program operation, requiring no external erase command. Factory pre-programming is available for high-volume applications.

The 24LC1025 is a serial EEPROM that stores data in floating-gate transistor cells and communicates via the I2C protocol. Here is how it works:

1. EEPROM Memory Array: The 1 Mbit memory array is organized as 128,000 x 8 bits. Data is stored in floating-gate MOSFET cells where the gate is electrically isolated by an oxide layer. Programming injects electrons onto the floating gate (changing the threshold voltage to represent a ‘0’), and erasing removes electrons (restoring the ‘1’ state). The data is non-volatile – it is retained for over 200 years without power.

2. I2C Interface: Communication is via a standard 2-wire I2C bus:
– SCL (Serial Clock): Clock signal generated by the master (MCU)
– SDA (Serial Data Address): Bidirectional data line
Both lines require pull-up resistors (typically 4.7 kΩ to Vcc). The 24LC1025 operates as a slave device. It supports I2C Standard Mode (100 kHz) and Fast Mode (400 kHz). Schmitt triggers on both inputs reject noise and slow-rising edges.

3. Device Addressing: The 7-bit device address is:
– 4 MSBs: ‘1010’ (fixed for 24-series EEPROMs)
– Next 2 bits: A1, A0 (set by external address pins)
– Bit 2 (A2): internally tied to Vcc (always 1)
– LSB: R/W bit (1 = read, 0 = write)
With 2 address pins, up to 4 devices can share the same bus.

4. Write Operation:
– Byte Write: Master sends device address (write), 17-bit memory address (2 byte address phase, using the A16 bit as part of the device address byte), then 1 data byte. EEPROM writes the byte into the addressed location. Self-timed write cycle takes up to 5 ms.
– Page Write: Similar to byte write, but master can send up to 128 data bytes after the address. All bytes are loaded into the 128-byte page write buffer, then programmed simultaneously into the selected page. Writes within a page boundary maximize efficiency.
– Acknowledge Polling: After initiating a write, the master can poll the device by sending its address. No ACK means write is still in progress; ACK means write is complete.

5. Read Operation:
– Current Address Read: Reads from the address last accessed + 1. No address phase needed.
– Random Read: Master sends device address (write) + memory address (sets address pointer), then repeated start + device address (read). EEPROM outputs the data byte.
– Sequential Read: After any read operation, if master ACKs the data byte, the address pointer auto-increments and the next byte is output. Can read entire memory array in one operation.

6. Write Protection: When WP pin is high, the entire memory array is write-protected. Attempted write operations are ignored. WP low allows normal write operation. Provides hardware protection against accidental writes.

7. Power Management:
– Active (Read): 450 µA max at 5.5V, 400 kHz
– Standby: 5 µA max at 5.5V
– Low-voltage detection: internal power-on reset ensures proper startup and prevents writes at low supply voltage

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

    A0  1-+---+-8  Vcc
    A1  2-|   |-7  Vss (or N/C)
    WP  3-|   |-6  SCL
   GND  4-+---+-5  SDA

Note: Available in multiple package options. -I/P = 8-pin PDIP (through-hole), -I/SM = 8-pin SOIJ, -I/SN = 8-pin SOIC, -I/ST = 8-pin TSSOP, -I/MC = 8-pin DFN (surface mount). All have the same pinout. Industrial temperature range: -40°C to +85°C ambient. RoHS compliant, lead-free.

• Industrial Control and Factory Automation: PLC modules, industrial sensors, and fieldbus devices where large non-volatile storage is needed for configuration parameters, calibration data, device IDs, network settings, and event logs. The industrial temperature range and high reliability (200-year retention) meet the requirements of long-lifecycle industrial equipment.
• Automotive Electronics and Sensors: Automotive ECUs, sensor modules, and body electronics requiring storage of calibration data, vehicle configuration, and fault codes. Automotive-grade versions (AEC-Q100 qualified) are available. The I2C interface allows simple connection to the microcontroller, and the 1 Mbit capacity stores comprehensive error logs and tuning parameters.
• Consumer Electronics and Smart Home: Smart TVs, set-top boxes, home automation hubs, and IoT devices storing user preferences, Wi-Fi credentials, firmware parameters, and manufacturing data. The low standby current (5 µA) minimizes battery drain in always-on standby modes, and page writes enable fast bulk parameter updates.
• Data Storage and Configuration Memory: Motherboards, network cards, graphics cards, and other computer peripherals storing BIOS/UEFI configuration, MAC addresses, serial numbers, and board-level parameters. Hardware write protection (WP pin) prevents accidental corruption of critical factory-programmed data.
• IoT and Wireless Sensor Nodes: Battery-powered IoT devices and wireless sensor nodes storing sensor calibration coefficients, network parameters, and data logs for batch upload. The low active current (450 µA read) and 5 µA standby current minimize power consumption, extending battery life in energy-harvesting and battery-powered applications.
• Medical Devices and Equipment: Patient monitors, diagnostic equipment, and medical sensors storing device calibration, patient data logs, and configuration parameters. The high endurance (1M cycles) supports frequent data logging, and the non-volatile nature ensures data survives power loss in clinical environments.
• Networking and Telecom Equipment: Routers, switches, gateways, and optical transceivers storing configuration data, port parameters, firmware images, and statistical counters. Up to 4 devices can be cascaded on a single I2C bus for increased memory capacity, enabling modular designs with multiple EEPROMs per board.
• Power Supply and Battery Management: Battery chargers, power supply modules, and BMS (Battery Management Systems) storing battery parameters, charge cycles, manufacturing data, and calibration values. The 2.5 V to 5.5 V wide operating range works with various system supply voltages, and the I2C interface allows the MCU to read/write parameters during operation.