Matchline precharge architecture for self-reference matchline sensing

Patent metadata

Field	Value
Publication number	US-9583192-B1
Application number	US-201615164325-A
Country	US
Kind code	B1
Filing date	May 25, 2016
Priority date	May 25, 2016
Publication date	Feb 28, 2017
Grant date	Feb 28, 2017

Abstract

The present disclosure relates to content addressable memories (CAM), and more particularly, to a searchable CAM structure having self-reference matchline precharge and local feedback control and method of use. The present disclosure includes a structure which includes: a sense line connected to a sensing device; a feedback line connected to the sense line at a tap point between a first end and a second end of the sense line; and a local precharge controller connected to the tap point by the feedback line to control precharging of the sense line according to a state of the feedback line.

First claim

What is claimed:

1. A structure, comprising:
a sense line connected to a sensing device;
a feedback line connected to the sense line at a tap point between a first end and a second end of the sense line; and
a local precharge controller connected to the tap point by the feedback line to control precharging of the sense line according to a state of the feedback line.

2. The structure of claim 1 , wherein the sensing device further comprises an inverter connected to the tap point by the feedback line.

3. The structure of claim 2 , wherein:
the sensing device has a threshold, and, when a charge state of the feedback line reaches the threshold of the sensing device, the inverter turns off the precharging of the sense line; and
the local precharge controller has a threshold, and, when a charge state of the feedback line reaches the threshold of the local precharge controller, the local precharge controller turns off access to a voltage source.

4. The structure of claim 3 , wherein the threshold of the local precharge controller is greater than the threshold of the sensing device.

5. The structure of claim 2 , wherein the local precharge controller comprises an inverter having a threshold higher than a threshold of the inverter of the sensing device.

6. The structure of claim 2 , wherein the local precharge controller comprises a switch having a threshold higher than a threshold of the inverter of the sensing device.

7. The structure of claim 1 , wherein the local precharge controller turns off the precharging of the matchline before a global precharge signal received by the sensing device is ended.

8. A structure, comprising:
a global controller to output a global precharge signal;
a matchline connected to bit comparison transistors; and
a sense amplifier connected to the global controller and the matchline, the sense amplifier comprising a local precharge controller configured to locally precharge the matchline.

9. The structure of claim 8 , further comprising a feedback line connected to the matchline at a tap point between a first end of the matchline and a second end of the matchline to indicate a charge state of the individual matchline for local precharge control by the local precharge controller.

10. The structure of claim 9 , wherein the feedback line is connected to the local precharge controller, and the local precharge controller stops the precharge of a sense-line or the matchline according to a state of charge of the feedback line.

11. The structure of claim 10 , wherein the first end of the matchline is connected to the sense amplifier, and the tap point is about ⅓ to about ½ of the length of the matchline from the first end of the matchline.

12. The structure of claim 10 , wherein the sense amplifier further comprises an inverter connected to the feedback line, and the sense amplifier turns off charging of the matchline according to a state of charge of the feedback line.

13. The structure of claim 12 , wherein the local precharge controller comprises an inverter having a threshold higher than a threshold of the inverter of the sense amplifier.

14. The structure of claim 12 , wherein the local precharge controller comprises a switch having a threshold higher than a threshold of the inverter of the sense amplifier.

15. A method for determining a match or a mismatch on a matchline, the method comprising:
precharging a matchline connected to a sense amplifier; and
turning off the precharging of the matchline according to a charge state of a feedback line connected to the matchline.

16. The method of claim 15 , wherein the matchline is precharged to a threshold of an inverter connected to the matchline by the feedback line.

17. The method of claim 16 , wherein, upon reaching the threshold, the inverter turns off access of the matchline to a voltage source.

18. The method of claim 16 , wherein, upon reaching the threshold, the charge on the matchline distributes along the matchline to reach a threshold at a tap point, the tap point being located between a first end and a second end of the matchline, to turn off the precharging of the matchline.

19. The method of claim 15 , wherein the charge state of the feedback line is determined at a tap point located between a first end and a second end of the matchline.

20. The method of claim 19 , wherein the first end of the matchline is connected to the sense amplifier, and the tap point is about ⅓ to about ½ of the length of the matchline from the first end of the matchline.

Assignees

• Globalfoundries Inc

Inventors

• Arsovski Igor
• Fragano Michael T
• Maffitt Thomas M
• Houle Robert M

Classifications

• G11C7/12

  Bit line control circuits, e.g. drivers, boosters, pull-up circuits, pull-down circuits, precharging circuits, equalising circuits, for bit lines · CPC title

• G11C15/04 Primary

  using semiconductor elements · CPC title

• G11C7/08 Primary

  Control thereof · CPC title

• G11C15/00

  Digital stores in which information comprising one or more characteristic parts is written into the store and in which information is read-out by searching for one or more of these characteristic parts, i.e. associative or content-addressed stores · CPC title