MBIST

MBIST stands for Memory Built-In Self-Test. It is a specialized form of built-in self-test designed to exercise and validate memory arrays within integrated circuits, such as SRAMs and embedded memories, during manufacturing and, in some cases, in production or field environments. The goal is to detect manufacturing faults early and reduce reliance on external test equipment.

A typical MBIST architecture includes the memory array under test, a test controller, an address generator, a data pattern generator (often based on a pseudo-random sequence using linear feedback shift registers), and a data comparator or checker. The controller orchestrates test passes, loads test patterns and address sequences, and collects results. The data checker compares read data from the memory with the expected values, signaling failures to status registers and potentially recording failing addresses or patterns for diagnosis. Many MBIST designs expose interfaces for testing control and status via standard test access mechanisms, such as JTAG, or through dedicated internal interfaces.

MBIST employs a variety of test algorithms, frequently using deterministic or pseudo-random patterns to cover a broad range of fault types. Common target faults include stuck-at, transition, coupling, and pattern-sensitive faults. March-type tests, such as MARCH C- or MATS, or bespoke sequences, are used to achieve high fault coverage with manageable hardware overhead. MBIST can run as a self-contained unit, supporting single-shot or multi-pass operations and can be integrated with ECC systems for memory reliability.

Applications of MBIST span ASICs, System-on-ChiP designs, and programmable logic, where embedded memory requires efficient, autonomous testing. It helps shorten test time, reduce external tooling, and improve yield by verifying memory integrity at various stages of the production and deployment cycle.