Single-ended sense amplifier with dual feedback and a latching disable

Abstract

An integrated circuit is disclosed with a logic network having an output coupled to a sense node and having a virtual ground node, and with a sense amplifier having a sensing circuit coupled to the sense node to provide an output signal, charging and discharging feedback circuits coupled to the sense node that limit the swing of the sense amplifier, and an enable control to enable and disable the sense amplifer. In one embodiment in a CMOS integrated circuit a parallel network of n-channel transistors has an output connected to a sense node of a sense amplifier. A sensing inverter and a feedback inverter are connected to this sense node. The switchpoint of the feedback inverter is substantially higher than the switchpoint of the sensing inverter. A charging n-channel transistor is connected between the sense node and a power supply for charging the sense node, and the output of the feedback inverter is connected to the gate of the charging transistor. A discharging n-channel transistor is connected in series between the parallel network and ground. The gate of the discharging transistor is coupled to the sense node. The sense amplifier can enter a power-saving disable mode, and entry is controlled by a sense amplifier enable signal. This mode has two possible states corresponding to the state of the sense amplifier immediately preceding disablement and enables the sense amplifier to avoid output glitches when leaving the disabled mode. The sense amplifier uses two negative feedback loops, including the charging and discharging n-channel transistors, to limit the swing on the sense node, and this swing is substantially independent of the number of parallel transistors that are conductive.