Microchip 24LC65/P 64K I²C Serial EEPROM: Features and Application Design Guide
The Microchip 24LC65/P is a 64 Kbit Electrically Erasable PROM (EEPROM) designed for reliable non-volatile data storage in a wide range of applications. Its utilization of the ubiquitous I²C (Inter-Integrated Circuit) serial communication protocol makes it an ideal choice for microcontroller-based systems, offering a simple two-wire interface that minimizes board space and interconnect complexity.
Key Features and Specifications
At its core, the 24LC65/P provides 8192 x 8 bits of organized memory. This structure makes it particularly suitable for storing data records, configuration parameters, and calibration constants. A critical feature of this device is its built-in write-protection scheme. The WP (Write Protect) pin, when tied to VCC, activates hardware write protection for the entire memory array, safeguarding critical data from accidental overwrites.
The device supports a 2-wire serial interface (I²C), comprising a bidirectional Serial Data (SDA) line and a Serial Clock (SCL) line. This interface is compatible with both 100 kHz and 400 kHz clock speeds, allowing for flexible communication with various host controllers. Furthermore, the 24LC65/P is designed for low-power operation, making it an excellent fit for battery-powered and portable devices. It features a low standby current and an active current of just 1 mA (max) during a read operation.
To facilitate design-in across multiple devices on the same bus, the 24LC65/P offers programmable device addressing using three address pins (A0, A1, A2). This allows up to eight 24LC65 devices to be connected on the same I²C bus, effectively expanding the available non-volatile memory to 512 Kbits.
Application Design Guide
Successful integration of the 24LC65/P hinges on several key design considerations:
1. Hardware Connection: The I²C bus requires pull-up resistors on both the SDA and SCL lines. The value of these resistors (typically between 2.2 kΩ and 10 kΩ) must be chosen based on the bus capacitance and desired rise time to ensure signal integrity. The VCC pin must be decoupled with a 100 nF ceramic capacitor placed close to the device.
2. Sequential Read Operation: One of the most powerful features for data retrieval is the sequential read function. After providing a random memory address to start from, the host can continue reading subsequent bytes without sending another address. The internal address pointer automatically increments after each read, allowing for rapid data stream output.
3. Page Write Operation: For efficient data writing, the memory is arranged in 64-byte pages. The device can write up to 64 bytes (one page) of data in a single write cycle, which lasts a maximum of 5 ms. Attempting to write more than one page of data in a single sequence will cause the address pointer to wrap around to the beginning of the page, potentially overwriting previously written data. Firmware must be designed to manage page boundaries correctly.
4. Acknowledge Polling: After initiating a write cycle, the device will not respond until the cycle is complete. The host can use acknowledge polling to determine when the write is finished. By sending a START condition followed by the device address, the host waits until it receives an ACK from the EEPROM, signaling it is ready for the next operation.
5. Noise Protection: The device incorporates robust noise immunity filters on the SDA and SCL lines to reject spurious pulses. For systems operating in electrically noisy environments, ensuring clean power and signal traces is paramount.
ICGOOODFIND
The Microchip 24LC65/P stands out as a highly reliable and easy-to-implement solution for non-volatile memory needs. Its combination of a standardized I²C interface, hardware data protection, low-power operation, and flexible addressing makes it a versatile and robust choice for designers across consumer electronics, industrial systems, and IoT applications.
Keywords: I²C Interface, Serial EEPROM, Non-volatile Memory, Page Write, Hardware Write Protection
