Semiconductor memory device with dataline undershoot detection and reduced read access time

Abstract

An apparatus and method for use in a semiconductor memory device to detect dataline undershoot. The detection of dataline undershoot is used to reduce dataline recovery time and output buffer recovery time, thereby reducing read access time in the memory device. A dataline coupled between a memory array and a sensing amplifier is applied to one input of a voltage comparator and compared to a reference voltage. The presence of undershoot on the dataline causes the dataline voltage to drop below the reference voltage, resulting in a transition in the comparator output. This transition triggers a pulse generator which supplies a pulse to the gate of a field effect transistor coupled between the dataline and an equalization voltage centered in a sensing window of the sensing amplifier. The pulse turns on the transistor such that the dataline is coupled to the equalization voltage, resulting in a rapid pull-up of the dataline and a significant reduction in dataline undershoot and thereby the dataline recovery time. The detection of undershoot is also used to generate a second pulse which is applied to turn off or tri-state an output buffer of the memory device. This places the output buffer into a high impedance state during dataline undershoot which leads to a significantly reduced output buffer recovery time as well as reduced output buffer noise.

Dependencies are inferred from the claim text.