Integrated flash memory systems and methods for load compensation
View Patent ↗Systems and methods are disclosed including features that compensate for variations in the magnitude of supply voltages used in memory arrays. According to some aspects, compensation circuits may provide a tunable current-limiting load for data columns, where the load can be tuned to dynamically compensate for variations in supply voltage. In certain aspects, a compensation circuit may employ an operational amplifier configured as a voltage follower. The voltage follower compensates for any variations in supply voltage, forcing a constant voltage drop across the load element(s), thus maintaining a constant load. Other circuits may also be included, such as precharge circuits, clamp circuits, buffer circuits, trimming circuit, and sense amplifier circuits with sensed body effect. System-On-Chip integrated system aspects may include a microcontroller, a mixed IP, and a flash memory system having functionality and blocks that interface and interoperate with each other for load compensation.
1. A multilevel memory system configured to detect a voltage level stored in a multilevel memory cell, comprising:
a memory sensing circuit connected to the multilevel memory cell and having a voltage supply terminal,
a load element connected between the voltage supply terminal and the multilevel memory cell, the load element providing a load for the memory sensing circuit as a function of a voltage drop across at least a portion of the load element and a current through the load element;
a load compensation circuit connected to the load element and configured to maintain the load by compensating for a load variation of the load; and
a precharge circuit in electrical communication with the memory sensing circuit, the precharge circuit configured to transmit a precharge to the memory sensing circuit so as to reduce a settle time of the memory sensing circuit.
2. The system of claim 1 wherein the load element is an enhancement PMOS transistor.
3. The system of claim 1 wherein the load element is a native PMOS transistor.
4. The system of claim 1 wherein the load element is a slightly depleted PMOS transistor.
5. The system of claim 1 wherein the load variation is a load variation due to at least one of a variation in a magnitude of a voltage applied at the voltage supply terminal, a variation in a temperature of the load element, or a variation in a fabrication of the load element.
6. The system of claim 1 wherein the load compensation circuit is further configured to maintain the load at a predetermined value.
7. The system of claim 1 wherein the load element is a PMOS transistor.
8. The system of claim 7 wherein the load compensation circuit is configured as a voltage follower circuit configured to maintain the load by maintaining a voltage drop across a portion of the PMOS transistor.
9. A multi-level memory system configured to detect a voltage level stored in a multilevel memory cell, comprising:
a memory sensing circuit connected to the multilevel memory cell and configured to generate an output voltage signal corresponding to data stored in the multilevel memory cell; and
a comparator circuit having a first transistor and a second transistor, the comparator circuit configured to compare the output voltage signal to a reference voltage signal according to a difference between a bulk gain of the first transistor and a bulk gain of the second transistor, the gain of the first transistor determined according to the reference voltage signal, and the gain of the second transistor determined according to the output voltage signal;
a precharge circuit in electrical communication with the memory sensing circuit, the precharge circuit configured to transmit a precharge to the memory sensing circuit so as to reduce a settle time of the memory sensing circuit.
10. The system of claim 9 wherein the first transistor has a first bulk terminal and the second transistor has a second bulk terminal, the comparator circuit receiving the reference voltage signal at the first bulk terminal so as to determine the gain of the first transistor according to a body effect at the first transistor, and receiving the output voltage signal at the second bulk terminal so as to determine the gain of the second transistor according to a body effect at the second transistor.
11. The system of claim 10 wherein the first transistor is a first PMOS transistor having a first drain terminal and a first source terminal, and the second transistor is a second PMOS transistor having a second drain terminal and a second source terminal, the first and second source terminals in electrical communication with a voltage source, and the multilevel memory sensing system further comprising:
a third PMOS transistor having a third source terminal in electrical communication with the voltage source, and a third drain terminal;
a current mirror circuit connected to the first and second drain terminals, and configured to mirror current through the first PMOS transistor into the second PMOS transistors; and
an output terminal of the comparator circuit, the output terminal connected to the third drain terminal.
12. The system of claim 10 wherein the first transistor is a first PMOS transistor having a first drain terminal and a first source terminal, and the second transistor is a second PMOS transistor having a second drain terminal and a second source terminal, the first and second source terminals in electrical communication with a voltage source, and the multilevel memory sensing system further comprising:
a third PMOS transistor having a third source terminal in electrical communication with the voltage source, and a third drain terminal;
a fourth PMOS transistor having a fourth source terminal in electrical communication with the voltage source, and a fourth drain terminal;
a current mirror circuit connected to the first, second, and third drain terminals, and configured to mirror current through the first PMOS transistor into the second, and third PMOS transistors; and
an output terminal of the comparator circuit, the output terminal connected to the fourth drain terminal.
13. The system of claim 9 wherein the precharge circuit further comprises a plurality of resistors configured in electrical series so as to transmit the precharge according to a ratio of the resistances of the resistors.
14. The system of claim 9 wherein the memory system is non-volatile.
15. The system of claim 9 wherein the memory sensing circuit is configured to generate an output voltage signal corresponding to data stored in the multilevel memory cell, the output voltage having an associated noise, the system further comprising:
a buffer circuit having an input terminal connected to the memory sensing circuit and configured to receive the output voltage signal, and having an output terminal, the buffer circuit configured to decouple the output voltage signal from the associated noise so as to form a decoupled output voltage signal, and configured to transmit the decoupled output voltage signal at the output terminal.
16. A multi-level memory system configured to detect a voltage level stored in a multilevel memory cell, comprising:
a memory sensing circuit connected to the multilevel memory cell and configured to generate an output voltage signal corresponding to data stored in the multilevel memory cell; and
a comparator circuit having a first transistor and a second transistor, the comparator circuit configured to compare the output voltage signal to a reference voltage signal according to a difference between a bulk gain of the first transistor and a bulk gain of the second transistor, the gain of the first transistor determined according to the reference voltage signal, and the gain of the second transistor determined according to the output voltage signal;
a clamp circuit in electrical communication with the memory sensing circuit, the clamp circuit configured to apply a clamp voltage to the memory sensing circuit so as to maintain a voltage within the memory sensing circuit.
17. The system of claim 16 wherein the clamp circuit further includes a voltage source terminal and a PMOS transistor coupled between the voltage source terminal and the multilevel memory cell.
18. The system of claim 16 wherein the memory sensing circuit is configured to generate an output voltage signal corresponding to data stored in the multilevel memory cell, the output voltage having an associated noise, the system further comprising:
a buffer circuit having an input terminal connected to the memory sensing circuit and configured to receive the output voltage signal, and having an output terminal, the buffer circuit configured to decouple the output voltage signal from the associated noise so as to form a decoupled output voltage signal, and configured to transmit the decoupled output voltage signal at the output terminal.
19. The system of claim 16 wherein the clamp circuit further includes a voltage source terminal and an NMOS transistor coupled between the voltage source terminal and the multilevel memory cell.
20. The system of claim 16 wherein the memory system is non-volatile.
21. The system of claim 16 wherein the first transistor has a first bulk terminal and the second transistor has a second bulk terminal, the comparator circuit receiving the reference voltage signal at the first bulk terminal so as to determine the gain of the first transistor according to a body effect at the first transistor, and receiving the output voltage signal at the second bulk terminal so as to determine the gain of the second transistor according to a body effect at the second transistor.
22. The system of claim 21 wherein the first transistor is a first PMOS transistor having a first drain terminal and a first source terminal, and the second transistor is a second PMOS transistor having a second drain terminal and a second source terminal, the first and second source terminals in electrical communication with a voltage source, and the multilevel memory sensing system further comprising:
a third PMOS transistor having a third source terminal in electrical communication with the voltage source, and a third drain terminal;
a current mirror circuit connected to the first and second drain terminals, and configured to mirror current through the first PMOS transistor into the second PMOS transistors; and
an output terminal of the comparator circuit, the output terminal connected to the third drain terminal.
23. The system of claim 21 wherein the first transistor is a first PMOS transistor having a first drain terminal and a first source terminal, and the second transistor is a second PMOS transistor having a second drain terminal and a second source terminal, the first and second source terminals in electrical communication with a voltage source, and the multilevel memory sensing system further comprising:
a third PMOS transistor having a third source terminal in electrical communication with the voltage source, and a third drain terminal;
a fourth PMOS transistor having a fourth source terminal in electrical communication with the voltage source, and a fourth drain terminal;
a current mirror circuit connected to the first, second, and third drain terminals, and configured to mirror current through the first PMOS transistor into the second, and third PMOS transistors; and
an output terminal of the comparator circuit, the output terminal connected to the fourth drain terminal.
24. A multilevel memory system configured to detect a voltage level stored in a multilevel memory cell, comprising:
a memory sensing circuit connected to the multilevel memory cell and having a voltage supply terminal,
a load element connected between the voltage supply terminal and the multilevel memory cell, the load element providing a load for the memory sensing circuit as a function of a voltage drop across at least a portion of the load element and a current through the load element;
a load compensation circuit connected to the load element and configured to maintain the load by compensating for a load variation of the load; and
a clamp circuit in electrical communication with the memory sensing circuit, the clamp circuit configured to apply a clamp voltage to the memory sensing circuit so as to maintain a voltage within the memory sensing circuit.
25. The system of claim 24 wherein the load element is an enhancement PMOS transistor.
26. The system of claim 24 wherein the load element is a native PMOS transistor.
27. The system of claim 24 wherein the load element is a slightly depleted PMOS transistor.
28. The system of claim 24 wherein the load variation is a load variation due to at least one of a variation in a magnitude of a voltage applied at the voltage supply terminal, a variation in a temperature of the load element, or a variation in a fabrication of the load element.
29. The system of claim 24 wherein the load compensation circuit is further configured to maintain the load at a predetermined value.
30. The system of claim 24 wherein the load element is a PMOS transistor.
31. The system of claim 30 wherein the load compensation circuit is configured as a voltage follower circuit configured to maintain the load by maintaining a voltage drop across a portion of the PMOS transistor.