Patent ID: 9576655
Date: 2017-02-21
CPC Classifications: G11C

Claim:
1. An apparatus for programming at least one multi-level Phase Change Memory (PCM) cell having a first terminal and a second terminal, the apparatus comprising: a measuring device; a bitline pulse generator; a selector device; and a programmable controller configured to control the PCM cell to have a cell state by applying a first voltage pulse to the first terminal of the PCM cell and applying a second voltage pulse to the second terminal of the PCM cell, said cell state being defined at least by a corresponding resistance level, wherein said programmable controller receives a signal representing a reference resistance value defining a target resistance level for said PCM cell, and receives a further signal representing an actual resistance value of said PCM cell, said applying said first voltage pulse and applying said second voltage pulse is based on said actual resistance value of the PCM cell and said received reference resistance value, said programmable controller is configured to generate an initial pair of first and second voltage pulses, the first voltage pulse including a bitline voltage pulse for application to the first terminal and the second voltage pulse including a wordline voltage pulse for application to the second terminal, said measuring device configured to measure the actual resistance value of the PCM cell, and provide the measured actual resistance value to said programmable controller, said PCM cell includes an access entity configured to control an access to the PCM cell, said programmable controller applying said wordline voltage pulse to a control terminal of said access entity and applying said bitline voltage pulse to a bitline, said PCM cell being coupled between said bitline and said access entity, said wordline voltage pulse and said bitline voltage pulse are controlled by a difference value of the actual resistance value and the reference resistance value, said programmable controller is configured to said bitline pulse generator is configured to provide the bitline voltage pulses to the PCM cell in dependence on said first control signal, and said selector device is configured to select the wordline voltage pulse from a number of defined wordline voltage pulses in dependence on said second control signal.