In a static random access memory (SRAM), a data bit read from or written into a memory cell is typically represented as a differential voltage between a bit line pair that is coupled to the memory cell. Multiple memory cells are coupled to one bit line pair. During a write cycle of the memory, the data bit is driven onto the bit line pair as a differential voltage. The differential voltage is large enough to overwrite an existing value in the selected memory cell. When a read cycle occurs, the selected memory cell places a data bit stored within the selected memory cell on the bit line pair as a relatively small differential voltage.
Before a read cycle can occur, the differential voltage that existed on the bit line pair must be reduced to a level low enough so that the data is not erroneously written into a memory cell during the read cycle. The differential voltage must be reduced quickly at the end of the write cycle so that the read cycle is not unnecessarily extended. This process is called write recovery.
Write recovery is typically achieved by using circuits known as bit line loads. The bit line load precharges and/or equalizes the differential voltage on the bit line pair to which it is coupled. In some memories, the bit line pairs are maintained in a precharged state by the bit line loads, in which case the bit line loads may function to recharge the bit line pairs.
During bit line equalization, the bit line load couples one bit line of the bit line pair to the other bit line. To "precharge" the bit line pair, each bit line is coupled to a power supply voltage terminal to increase the voltage on the bit line pair to a predetermined voltage.
BICMOS (bipolar-complementary metal-oxide semiconductor) technology is commonly used in the bit line loads because of their high speed operation and relatively low power supply consumption. However, as increasingly higher access times are required, it is important to precharge and equalizes the bit line pairs of the memory, such as during a write recovery, as quickly as possible.