ATSHA204A-SSHDA-T is a SHA-256 secure authentication chip from Microchip (Atmel), implementing NIST SP 800-90 Alea entropy source, ARC4 encryption algorithm and SHA-256 hash algorithm in hardware. With 10Kb built-in EEPROM for key, configuration and user data storage, the chip communicates with host MCU via single-wire interface (SWI) or I2C, widely used in consumer electronics authentication (headphones, gamepads, chargers), IoT device identity, and automotive LIN/CAN node security.

The core value of this chip is encapsulating the entire HMAC-SHA-256 symmetric authentication protocol computation in hardware, so the private key is never exposed on the bus. The host sends a random challenge, the ATSHA204A computes the response using its private key and SHA-256 algorithm, and only a host that knows the correct key can complete mutual authentication - ensuring accessory authenticity, preventing cloning and man-in-the-middle attacks.

Compared to pure software security implementations, ATSHA204A provides protection against key extraction attacks: after keys are written through a secure channel at the factory, no external interface can read them back - they can only be used to generate authentication responses. This makes it the preferred solution for anti-piracy, anti-cloning and device identity authentication.

Note: For detailed electrical parameters, security authentication flow and communication protocol, refer to the Microchip official datasheet (DS84404). Specifications subject to change without notice. Design engineers should verify all parameters before final design.

ATSHA204A-SSHDA-T uses SOIC-8 Wide Body package (Small Outline Integrated Circuit, SSHD suffix = SOIC-8 Wide Body), typical dimensions 5.0mm × 6.0mm × 1.5mm (L×W×H), pin pitch 1.27mm, 8 functional pins.

The SOIC-8 Wide Body package offers wider pin spacing than standard SOIC-8, suitable for applications requiring larger solder pad spacing or manual soldering. This package is fully compatible with standard PCB pads and can be mounted using standard SMT processes.

The ATSHA204A-SSHDA-T in SOIC-8 package has 8 pins, pin assignments as follows (top view, counter-clockwise from lower-left):

• Pin 1 - VCC (Power): Supply voltage input, recommended 2.0V~5.5V. Place a 100nF decoupling capacitor between VCC and GND near the chip to suppress power supply noise.
• Pin 2 - SDA / DATA (Data): In SWI mode: single-wire data interface (connect to host MCU GPIO); in I2C mode: I2C data line (SDA). The chip receives host commands and returns authentication responses via this pin.
• Pin 3 - SCL / SDA (Clock/Second Data): In SWI mode: leave open or connect to GND; in I2C mode: I2C clock line (SCL).
• Pin 4 - NC (No Connect): Internally unconnected; leave floating.
• Pins 5-7 - GND (Ground): Chip ground pins, all tied to system ground. A complete PCB ground plane is recommended to minimize ground impedance noise.
• Pin 8 - VCC (Power): Second VCC pin, internally connected to Pin 1. Dual-pin power supply reduces pin current density.

The following alternative parts are listed for reference. Before selecting an alternative, verify communication interface, supply voltage, security algorithm compatibility, and software API differences.

Package Comparison

Selection Tips: ATSHA204A-SSHDA-T uses SHA-256 symmetric encryption, suitable for cost-sensitive applications where the host MCU can securely store the shared key. ATECC508A uses ECC asymmetric encryption with simpler key management but higher cost. DS28C36/DS28E30 are Maxim/ADI solutions, suitable for designs already using the Maxim security ecosystem. Verify communication interface (SWI/I2C/1-Wire), operating voltage and software API compatibility before selection.

Microchip Technology Inc. (NASDAQ: MCHP), headquartered in Chandler, Arizona, USA, is a leading global supplier of microcontrollers, analog devices and Flash-IP solutions. Microchip acquired Atmel to gain the industry-leading AVR microcontroller and ATAES/ATSHA secure chip product lines, with the ATSHA204A series being a benchmark product in the secure authentication chip market.

Microchip's CryptoAuthentication family covers the full range from SHA-256 symmetric authentication (ATSHA204A) to ECC asymmetric encryption (ATECC508A/608A), providing a unified software API (ATCA/ATECBlib) that simplifies cross-product migration. All secure chips support secure key programming services (AT88SCxxx-ND, ATECC-XSTO series), helping customers securely inject keys during production and preventing key leakage in the supply chain.