Programmable current for correlated electron switch

• US 9,748,943 B2
• Filed: 08/13/2015
• Issued: 08/29/2017
• Est. Priority Date: 08/13/2015
• Status: Active Grant

• Current Assignee: Arm Limited (SoftBank Group Corp.)
• Original Assignee: Arm Limited (SoftBank Group Corp.)
• Inventors: Sandhu, Bal S., Lattimore, George McNeil, Aitken, Robert Campbell
• Primary Examiner(s): Donovan, Lincoln
• Assistant Examiner(s): CHENG, DIANA
• Application Number:
  US14/826,091
• Publication Number:
  US 20170047919A1
• Time in Patent Office: 747 Days
• Field of Search: 327378, 365148, 365159, 365163
• CPC Class Codes: G11C 13/0007 comprising metal oxide memory material, e.g. perovskites
• CPC Class Codes: G11C 13/0069 Writing or programming circuits or methods
• CPC Class Codes: G11C 2013/0078 Write using current through the cell
• CPC Class Codes: G11C 29/021 in voltage or current generators
• CPC Class Codes: G11C 29/028 with adaption or trimming of parameters
• CPC Class Codes: H03K 17/14 Modifications for compensating variations of physical values, e.g. of temperature
• CPC Class Codes: H10N 70/20 Multistable switching devices, e.g. memristors
• CPC Class Codes: H10N 70/8833 Binary metal oxides, e.g. TaOx
• CPC Class Codes: H10N 70/8845 Carbon or carbides
• CPC Class Codes: H10N 99/03 Devices using Mott metal-insulator transition, e.g. field effect transistors

Abstract

Subject matter disclosed herein may relate to programmable current for correlated electron switches.

Claims

1. A method, comprising:

providing a programmable current to a correlated electron switch at least in part to cause a transition in the correlated electron switch from a first impedance state to a second impedance state; and

providing a reference voltage output to be utilized in conjunction with the programmable current to cause the transition in the correlated electron switch from the first impedance state to the second impedance state at least in part in response to an assertion of a write enable signal and at least in part in response to an assertion of a set or reset signal.

2. The method of claim 1, wherein the providing the programmable current to the correlated electron switch comprises generating the programmable current in accordance with a digital code.

3. The method of claim 2, wherein the digital code specifies a particular current level of a plurality of current levels available from a programmable current source.

4. The method of claim 3, wherein the generating the programmable current in accordance with the digital code comprises generating a programmable current having a level that is a multiple of a unit current level, wherein the multiple is determined at least in part by the digital code.

5. The method of claim 3, wherein the first impedance state comprises a relatively higher impedance state and the second impedance state comprises a relatively lower impedance state, and wherein the generating the programmable current in accordance with the digital code comprises generating a current sufficient to achieve a set condition to transition the correlated electron switch from the relatively higher impedance state to the relatively lower impedance state in accordance with a first digital code.

6. The method of claim 3, wherein the first impedance state comprises a relatively lower impedance state and the second impedance state comprises a relatively higher impedance state, and wherein the generating the programmable current in accordance with the digital code comprises generating a current sufficient to achieve a reset condition to transition the correlated electron switch from the relatively lower impedance state to the relatively higher impedance state in accordance with a second digital code, wherein the second digital code signifies a current greater than that signified by the first digital code.

7. The method of claim 2, wherein the digital code comprises a first plurality of bits to specify a current level substantially sufficient to cause the transition in the correlated electron switch from the first impedance state to the second impedance state, and wherein the digital code further comprises a second plurality of bits to specify a current level to compensate for variations in process, voltage, and/or temperature for the correlated electron switch.

8. An apparatus, comprising:

a programmable current source to generate a current for a correlated electron switch at least in part to cause a transition in the correlated electron switch from a first impedance state to a second impedance state; and

a voltage source to provide a reference voltage output to be utilized in conjunction with the programmable current to cause the transition in the correlated electron switch from the first impedance state to the second impedance state at least in part in response to an assertion of a write enable signal and at least in part in response to an assertion of a set or reset signal.

9. The apparatus of claim 8, wherein the programmable current source to generate the current for the correlated electron switch in accordance with a digital code.

10. The apparatus of claim 9, wherein the digital code to specify a particular current level of a plurality of current levels available from the programmable current source.

11. The apparatus of claim 10, wherein the programmable current source to comprise a unit current source coupled to digital-to-analog current converter.

12. The apparatus of claim 11, wherein to generate the current for the correlated electron switch, the digital-to-analog current converter to generate a current that is a multiple of a unit current level in accordance with the digital code.

13. The apparatus of claim 12, wherein the unit current source to comprise a current mirror circuit.

14. The apparatus of claim 13, wherein the digital-to-analog current converter to comprise a binary weighted digital-to-analog current converter.

15. The apparatus of claim 10, wherein the digital code to comprise a first plurality of bits to specify a current level substantially sufficient to cause the transition in the correlated electron switch from the first impedance state to the second impedance state.

16. The apparatus of claim 15, wherein the digital code further to comprise a second plurality of bits to specify a current level to compensate for variations in process, voltage, and/or temperature for the correlated electron switch.

17. An apparatus, comprising:

a correlated electron switch coupled to an output of a current mirror circuit;

a first conductive element to couple the current mirror circuit to a programmable current source at least in part in response to an enable signal, wherein the first conductive element is coupled to the programmable current source at a first node, and wherein the current mirror circuit to generate a reference current to cause at least in part a transition in the correlated electron switch from a first impedance state to a second impedance state;

a second conductive element to couple the first node to a voltage output node at least in part in response to a read signal, wherein the voltage output node is coupled to the correlated electron switch;

a third conductive element to couple a supply voltage signal to a third node at least in part in response to a set signal;

a fourth conductive element to couple a reference voltage signal to the third node at least in part in response to a reset signal;

a fifth conductive element to couple the third node to the voltage output node at least in part in response to a write enable signal; and

wherein the supply voltage is to be conducted to the voltage output node at least in part in response to the set signal and the write enable signal, and wherein the reference voltage is to be conducted to the voltage output node at least in part in response to the reset signal and the write enable signal.

18. The apparatus of claim 17, wherein the programmable current source comprises a plurality of individually selectable current stages, wherein individual current stages of the plurality of individually selectable current stages comprise a selector and a current source.

19. The apparatus of claim 18, wherein the selector to comprise a conductive element to conduct at least in part in response to a select signal corresponding to a bit of a digital code.

20. The apparatus of claim 17, wherein the digital code comprises a first plurality of bits to specify selection of one or more of the plurality of individually selectable current stages to cause the current mirror to generate a reference current level substantially sufficient to cause the transition in the correlated electron switch from the first impedance state to the second impedance state in conjunction with a voltage at the voltage output node, and wherein the digital code further comprises a second plurality of bits to specify selection of an additional one or more of the plurality of individually selectable current stages to compensate for variations in process, voltage, and/or temperature.

21. The apparatus of claim 17, wherein the conductive elements individually comprise one or more transistors.