Microchip 24LC32A-I/SN 32K I2C Serial EEPROM: Features and Application Design Guide

The Microchip 24LC32A-I/SN is a 32Kbit (4K x 8) serial Electrically Erasable PROM (EEPROM) that utilizes the ubiquitous I2C (Inter-Integrated Circuit) protocol for communication. This device is housed in a compact 8-lead SOIC (SN) package, making it an ideal solution for applications where board space is at a premium and non-volatile data storage is required. Its combination of capacity, reliability, and ease of use has made it a cornerstone component in countless embedded systems.

Key Features and Specifications

The 24LC32A boasts a set of features that cater to robust and versatile design requirements. Its 32Kbit memory array is organized as 4096 words of 8 bits each, providing ample space for storing configuration parameters, calibration data, transaction records, or other critical information. A critical advantage is its non-volatile nature, ensuring data retention even when system power is removed.

Communication is handled via a two-wire I2C serial interface, requiring only the Serial Data (SDA) and Serial Clock (SCL) lines. This significantly reduces the number of I/O pins required from the host microcontroller, simplifying board layout and design. The device supports a 400 kHz clock frequency, enabling efficient data transfer rates for most applications.

For system integrity, the chip includes hardware write-protection. When the WP (Write Protect) pin is tied to VCC, the entire memory array becomes protected against inadvertent write operations, safeguarding vital data. Furthermore, it features exceptional endurance, supporting 1,000,000 erase/write cycles per byte, and offers data retention of over 200 years.

Application Design Guide

Integrating the 24LC32A into a design is straightforward, but attention to a few key areas ensures optimal performance.

1. Circuit Connection: The I2C bus lines, SDA and SCL, require pull-up resistors to VCC. The value of these resistors (typically between 2.2kΩ and 10kΩ) depends on the bus capacitance and desired speed. The device address pins (A0, A1, A2) allow for up to eight identical EEPROMs to be connected on the same bus, providing addressability for expanded memory.

2. Power Supply Decoupling: A 0.1μF ceramic decoupling capacitor should be placed as close as possible between the VCC and VSS (ground) pins. This is essential for suppressing power supply noise and ensuring stable operation, especially during write cycles.

3. Write Protect (WP) Pin: This pin must be connected; it cannot be left floating. For normal read/write operation, connect it to VSS (GND). To enable hardware write protection for the entire memory array, connect it to VCC.

4. Software Protocol: The host microcontroller must implement the I2C protocol correctly. This involves:

Initiating a START condition.

Sending a control byte containing the 7-bit device address (1010[A2][A1][A0]) and the R/W bit.

Sending the 16-bit memory address (two bytes) to specify the target location for reading or writing.

For a write operation, sending one or more data bytes. The chip features a 32-byte page write buffer, allowing up to 32 bytes to be written in a single bus transaction, greatly improving efficiency.

Managing acknowledge (ACK) bits after each byte.

Terminating the transaction with a STOP condition.

5. Timing Considerations: After issuing a write command, the EEPROM enters an internally timed write cycle (tWC), typically lasting 5ms. During this time, the device will not acknowledge its address (a process known as polling). The master must wait for this cycle to complete before initiating the next communication.

ICGOOODFIND

The Microchip 24LC32A-I/SN is a highly reliable and efficient solution for adding non-volatile memory in I2C-based systems. Its ease of integration, robust feature set including hardware write-protection, and low power consumption make it an excellent choice for a vast range of applications, from consumer electronics and industrial controls to automotive systems and smart sensors.

Keywords: I2C EEPROM, Non-volatile Memory, Microchip 24LC32A, Serial Memory, Embedded Systems