Characterization and Translation of the PSI5 Protocol between ATE and DUT

Most MEMS devices to date feature a digital interface compatible with standard communication protocols like I2C and SPI. However, increasingly rigorous automotive requirements—particularly those related to real-time, deterministic communications, and safety-critical applications— have driven the development of a new communication bus known as PSI5 (Peripheral Sensor Interface 5). This protocol was initially developed for safety-critical airbag applications but is also widely used in other areas, including powertrain, chassis, and broader safety systems. PSI5 operates on a reliable two-wire current communication system, typically transmitting data at 125 kbps (up to 189 kbps). This efficient setup allows multiple distributed sensors in a vehicle to connect using only two wires for both power and data. My thesis, conducted at SPEA—a leader in testing microchips, MEMS, circuit boards, and electronic devices—focused on studying and characterizing the PSI5 protocol to establish communication between the SPEA ATE, which operates using the SPI protocol, and a DUT that communicates via PSI5, represented here by an airbag sensor. The primary challenges included handling this new protocol, managing the complex bus line composed of various cables, interposers, and connectors, and achieving high parallelism in testing—a feature not possible with the previous setup. The solution involved exploiting a transceiver to translate PSI5 communication into SPI, enabling reliable interaction between the Tester and the DUT. The work involved designing all necessary hardware, including a Load Board—an interface board mounted on the Tester, and where the Transceivers are placed—and a Demo Board, used to simulate the Socket Board (the board where the DUTs are positioned for testing). Additionally, a Test Program— a tester-specific program which consists in a set of predefined instructions used to evaluate the performance of a device or system—was developed to test various setup functionalities, such as acceleration data reading. To streamline future PSI5 application development, an application note was created, along with a C++ library implementing PSI5 functions.