A circuit and method for programming phase-change memory devices, such as chalcogenide memory (PRAM), are described. The invention is directed to an approach to programming PRAM elements from a reset state to a set state or from a set state to the set state. The invention provides a novel and nonobvious PRAM device and method in which a set pulse duration time is controlled by monitoring the state of the memory element during programming such as by comparing the voltage of a bit line with a reference voltage or comparing the cell resistance with a set state cell resistance. The duration of the set pulse is controlled in response to the detected state of the memory element. The result of the approach of the invention is the significant reduction in PRAM programming errors, such as those caused by a constant-duration set pulse, as well as reduction in programming time duration and power consumption.
RELATED APPLICATION
This application is a continuation of U.S. application Ser. No. 10/773,901, filed on Feb. 6, 2004, which relies for priority upon Korean Patent Application No. 03-0035564, filed on Jun. 3, 2003, the contents of which are herein incorporated by reference in their entirety.
An integrated circuit includes a memory element and a circuit. The circuit is configured to program the memory element by applying one or more pulses to the memory element until a sensed resistance of the memory element is within a range of a desired resistance. The one or more pulses have a parameter value that is modified for each subsequent pulse based on the parameter value for an immediately preceding pulse and on a difference between the sensed resistance of the memory element and the desired resistance.
