Report Number: CSL-TR-95-659
Institution: Stanford University, Computer Systems Laboratory
Title: High-Speed BiCMOS Memories
Author: Wingard, Drew Eric
Date: December 1994
Abstract: Existing BiCMOS static memories do not simultaneously combine the speed of bipolar memories with the low power and density of CMOS memories. Beginning with fundamentally fast low=swing bipolar circuits and zero-power CMOS storage latches, we introduce CMOS devices into the bipolar circuits to reduce the power dissipation without compromising speed and insert bipolar transistors into CMOS storage arrays to improve the speed without power nor density penalties. Replacing passive load resistors with switched PMOS transistors reduces the amount of power required to keep bipolar decoder outputs low. The access delay need not increase because the load resistance is quickly reduced via a low-swing signal when the decoder could switch. For ECL NOR decoders, we apply a variable BiCMOS current source that is simplified by carefully regulating the negative supply. We also develop techniques that improve the reading and writing characteristics of the CMOS-storage, emitter-access memory cell. The 16K-word 4-bit asynchronous CSEA memory was fabricated in a 0.8-micron BiCMOS technology and accesses in 3.7ns while using 1.75 W. An improved 64Kx4 design is simulated to run at 3.4ns and 2.3W. Finally, a synchronous 4Kx64 CSEA memory is estimated to operate at 2.5ns and 2.4W in the same process technology.