Secondary precharge mechanism for high speed multi-ported register files

Abstract

An electronic circuit has a register connected to a sense amplifier via a bitline (the sense amplifier has a primary precharge circuit), and a secondary precharge circuit also connected to the bitline. For bitlines that are relatively long, the secondary precharge circuit is located at a distal end of the bitline with respect to the sense amplifier. The secondary precharge circuit initially pulls up the voltage of the bitline, and the primary precharge circuit in the sense amplifier completes the precharging of the bitline. The secondary precharge circuit includes a cascode transistor coupled to the bitline via a feedback circuit. The feedback circuit is enabled during the precharge phase, when the bitline is discharged below a preset threshold. The threshold of the secondary precharge circuit can be set such that any skew between the precharge pulses of the secondary precharge circuit and the sense amplifier does not affect the falling bitline during the sense amplifier evaluate phase. Because of the initial surge of precharge from the secondary precharge circuit, the bitline is completely precharged in a shorter cycle time, allowing the sense amplifier to be operated at higher frequencies.