In memory operations, such as in static random access memory (SRAM) operations, read and write signal margins decrease as operational supply voltage VDD decreases. As technology advances, operational supply voltage VDD continues to decrease. As a result, speed performance has been sacrificed with VDD decreasing.
Transistors manufactured by a logic process are called logic transistors while transistors manufactured by a memory process are called memory transistors. In some approaches, both logic transistors and memory transistors are used in an SRAM macro. Both the logic process and the memory process result in slow, average, and fast transistors. For illustration, the condition in which a process provides slow, average, and fast transistors is called a slow condition or corner, an average corner, and a fast corner, respectively. In some approaches, speed performance of the SRAM macro is worst in a fast logic corner and a slow memory corner. To improve speed performance in average logic and memory corners, additional signal margins are added, which also compromises speed performance.
Like reference symbols in the various drawings indicate like elements.