A column read amplifier power-gating technique for DRAM devices and those devices
incorporating embedded DRAM which incorporate a power-down (or Sleep) mode of operation
which overcomes the deficiencies of conventional power-gating approaches by eliminating
the need for a large, separate power-gating transistor thereby saving on-chip area
yet still reducing power during Sleep Mode. In operation, the column select signal
YR is controlled such that it is driven below VSS during Sleep Mode when N-channel
pass transistors are used in the column read amplifier or to a supply voltage level
of VCC when P-channel devices are used instead. This significantly reduces the
current through the pass transistors and yet causes no reduction in the switching
speed of the column read amplifiers.