Matchline precharge architecture for self-reference matchline sensing
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.
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.