Secure Serial EEPROM Memory: Microchip AT24CS04-STUM-T Datasheet and Application Guide

In the rapidly evolving landscape of embedded systems and IoT, the need for secure, non-volatile memory is paramount. The Microchip AT24CS04-STUM-T stands out as a robust solution, combining reliable data storage with integrated security features. This 4-Mbit (512-Kbyte) serial EEPROM is designed for applications where data integrity and authenticity are critical, such as in medical devices, industrial controllers, smart meters, and consumable accessories.

Key Features and Datasheet Overview

Housed in a space-saving 8-lead TSSOP package, the AT24CS04-STUM-T operates across a broad voltage range (1.7V to 5.5V), making it suitable for both 3.3V and 5V systems. It communicates via the industry-standard I²C protocol, supporting speeds up to 1MHz, which ensures easy integration into existing designs.

The most distinguishing feature of this memory IC is its integrated 128-bit security register. This dedicated, one-time programmable (OTP) memory space can store a unique, factory-programmed or user-programmed serial number, cryptographic key, or other sensitive identifier. This provides a powerful hardware-based mechanism for:

Device Authentication: System hosts can challenge attached peripherals or consumables (e.g., a printer cartridge) to prove their authenticity by reading and verifying the secure key, effectively combating counterfeiting.

Secure Data Storage: The general-purpose EEPROM array offers a high endurance of 1,000,000 write cycles and a data retention period of 100 years, ensuring long-term reliability for configuration parameters, calibration data, and event logging.

The memory array is organized as 512 blocks of 128 bytes each. It includes built-in software and hardware write protection schemes. A dedicated Write Protect (WP) pin can be asserted to place the entire memory array (excluding the security register) in a read-only state, preventing accidental or malicious data corruption.

Application Guide and Design Considerations

Implementing the AT24CS04 is straightforward. The I²C bus requires only two bidirectional lines (SDA and SCL), significantly reducing board space and interconnect complexity. The device features three address pins (A0, A1, A2), allowing up to eight devices to be connected on the same bus, maximizing memory capacity.

A critical design consideration involves accessing the security register. The AT24CS04 has two unique I²C device addresses: one for accessing the main memory block (0x50 + chip select) and a separate address (0x58) for accessing the security register. This architecture physically isolates the sensitive data, requiring specific commands to read from the secure area, thereby enhancing system security.

When designing the PCB, it is essential to place decoupling capacitors close to the VCC and GND pins of the IC to ensure a stable power supply and minimize noise on the I²C lines. For applications in electrically noisy environments (e.g., industrial settings), implementing series termination resistors on the SDA and SCL lines can help improve signal integrity.

ICGOODFIND: The Microchip AT24CS04-STUM-T is an exceptional choice for designers seeking to add a layer of hardware security and reliable data storage to their products. Its combination of a large EEPROM array, a dedicated OTP security register, and robust packaging options makes it a versatile and critical component for securing the value chain and ensuring data integrity in modern electronic systems.

Keywords:

1. Secure Authentication

2. I²C EEPROM

3. Hardware Security

4. Non-volatile Memory

5. Device Integrity