Designing Drop-in Pseudo-Static Memories
Pseudo-static memories are designed to drop into the socket of a static random access memory (SRAM) even though the internal memory operation is not static. Two commercially available pseudo-static memories are PSRAM (pseudo-static RAM) and FRAM (ferroelectric random access memory). PSRAM targets slow SRAM applications and competes on a purely cost/bit basis. FRAM targets battery-backed SRAM (BBSRAM) applications and competes on the basis of system cost and logistics. FRAM also targets nonvolatile data acquisition applications, where it provides superior performance. This paper explains how these two pseudo-static memories succeed in their masquerade and make life easier for system designers.
The paper describes the techniques and circuits required to seamlessly drop pseudo-static memories into static memory slots, which have spurred the adoption of PSRAM in cellular phones and the migration from BBSRAM to FRAM.