Circuit and method for dynamically changing a trip point in a sensing inverter
A circuit and method for dynamically changing trip point voltage in a sensing inverter circuit. In one embodiment, the sensing inverter circuit includes: (1) a base inverter circuit couplable to logic-high and logic-low voltage sources at respective inputs thereof and configured to transition an output thereof from a previous logic-level voltage to a present logic-level voltage based on a logic value of an input voltage received by the base inverter circuit, and (2) a feedback circuit associated with the base inverter circuit and configured to employ the previous logic-level voltage to decouple one of the logic-high and logic-low voltage sources from one of the inputs and thereby shift a trip voltage of the base inverter circuit toward the input voltage.
1. A sensing inverter circuit, comprising:
a base inverter circuit couplable to logic-high and logic-low voltage sources at respective inputs thereof and configured to transition an output thereof from a previous logic-level voltage to a present logic-level voltage based on a logic value of an input voltage received by said base inverter circuit; and
a feedback circuit associated with said base inverter circuit and configured to employ said previous logic-level voltage to decouple one of said logic-high and logic-low voltage sources from one of said inputs and thereby shift a trip voltage of said base inverter circuit toward said input voltage.
2. The sensing inverter circuit as recited in claim 1 wherein said present logic-level voltage represents a logic value stored in a memory cell.
3. The sensing inverter circuit as recited in claim 2 wherein said logic-high and logic-low voltage sources are couplable when said memory cell is active.
4. The sensing inverter circuit as recited in claim 1 wherein said base inverter circuit comprises series coupled PMOS and NMOS transistors, said transistors having:
source terminals coupled respectively to said logic-high and logic-low voltage sources,
respective gate terminals coupled to a common input line, and
respective drain terminals coupled to a common output line.
5. The sensing inverter circuit as recited in claim 1 wherein said feedback circuit comprises an NMOS and PMOS transistor isolating said base inverter circuit from said logic-low and logic-high voltage sources respectively.
6. The sensing inverter circuit as recited in claim 5 wherein said previous logic-level voltage is applied at the gate terminals of said NMOS and PMOS transistors.
7. The sensing inverter circuit as recited in claim 1 wherein said present logic-level voltage is logically opposite of said previous logic-level voltage.
8. A method of adjusting a trip voltage in a sensing inverter circuit, comprising:
latching a first logic value from said sensing inverter circuit;
employing said first logic value in respectively coupling and decoupling first and second rail voltage sources to said sensing inverter circuit, thereby adjusting said trip voltage prior to sensing a second logic value; and
latching said second logic value.
9. The method as recited in claim 8 wherein said employing further comprises driving a PMOS transistor and a NMOS transistor for carrying out said coupling and decoupling.
10. The method as recited in claim 8 wherein said first and second rail voltage sources are a logic-high voltage source and a logic-low voltage source respectively.
11. The method as recited in claim 10 wherein said logic-high voltage source is coupled when said first logic value is high.
12. The method as recited in claim 8 wherein said first logic value and said second logic value represent consecutive data-reads from a column of a memory cell array.
13. The method as recited in claim 12 wherein said sensing inverter circuit is operable when said column is active.
14. The method as recited in claim 8 wherein said second logic value is logically opposite said first logic value.
15. A memory system configured to employ a sensing inverter circuit, comprising:
an array of memory cells;
an addressing circuit configured to activate a memory cell of said array of memory cells and associated with a specified memory address; and
a sensing inverter circuit, including:
a base inverter circuit couplable to logic-high and logic-low voltage sources at respective inputs thereof and configured to transition an output thereof from a previous logic-level voltage to a present logic-level voltage based on a logic value of an input voltage received by said base inverter circuit; and
a feedback circuit associated with said base inverter circuit and configured to employ said previous logic-level voltage to decouple one of said logic-high and logic-low voltage sources from one of said inputs and thereby shift a trip voltage of said base inverter circuit toward said input voltage.
16. The memory system as recited in claim 15 wherein said memory cell is coupled to an input terminal of said base inverter circuit via a bit-line.
17. The memory system as recited in claim 15 wherein said base inverter circuit comprises series coupled PMOS and NMOS transistors, said transistors having:
source terminals coupled respectively to said logic-high and logic-low voltage sources,
respective gate terminals coupled to a common input line, and
respective drain terminals coupled to a common output line.
18. The memory system as recited in claim 15 wherein said feedback circuit comprises an NMOS and PMOS transistor isolating said base inverter circuit from said logic-low and logic-high voltage sources respectively.
19. The memory system as recited in claim 15 wherein said previous logic-level voltage is applied to the gate terminals of said NMOS and PMOS transistors.
20. The memory system as recited in claim 15 wherein said present logic-level is logically opposite of said previous logic-level voltage.