Adaptive gate voltage regulation
View Patent ↗A memory device generates a select voltage and an unselect voltage on bit lines and generates a bit line select voltage having a magnitude less than the unselect voltage so that the application of the bit line select voltage to a gate of a transistor receiving the select voltage causes the transistor to conduct, and the application of the bit line select voltage to a gate of a transistor receiving the unselect voltage biases the transistor off.
1. A memory device, comprising:
a plurality of bit lines;
a plurality of column selectors connected to the bit lines and configured to receive a first voltage or a second voltage and output a select voltage or an unselect voltage to the bit lines;
a plurality of bit line selector transistors connected to the bit line, each bit line selector transistor defining a gate; and
a voltage regulator configured to generate a gate voltage on the gates of the bit line selector transistors that is less than the unselect voltage and that causes the bit line selector transistors receiving the select voltage from a bit line to conduct.
2. The memory device of claim 1 , wherein:
the first voltage is a ground voltage;
the second voltage is a power supply voltage; and
the unselect voltage is equal to the power supply voltage minus a column selector voltage.
3. The memory device of claim 2 , wherein:
the column selector voltage comprises a leakage current voltage drop.
4. The memory device of claim 1 , wherein:
the voltage regulator comprises:
a reference column selector configured to receive the second voltage; and
a bias circuit connected to the reference column selector and configured to generate a bias signal based on a leakage current of a column selector outputting the unselect voltage to a bit line.
5. The memory device of claim 4 , wherein:
the column selectors and reference column selectors are transistors and wherein the bias circuit is configured to bias the reference column selector in a sub-threshold region.
6. The memory device of claim 5 , wherein:
the bias circuit comprise a current source.
7. The memory device of claim 4 , further comprising:
a buffer amplifier connected to an output of the reference column selector and configured to generate the gate voltage based on the output of the reference column selector.
8. The memory device of claim 1 , further comprising:
a plurality of memory strings connected to the plurality of bit line selector transistors, each memory string defined by a plurality of memory cells.
9. The memory device of claim 8 , wherein:
the memory device comprises a flash memory device.
10. The memory device of claim 9 , wherein:
the flash memory device comprises a NAND flash array.
11. The memory device of claim 1 , wherein:
the gate voltage causes the bit line selector transistors receiving the select voltage from a bit line to conduct in a saturation condition.
12. A method, comprising:
generating a select voltage;
generating an unselect voltage;
determining an operational variance associated with generating the unselect voltage; and
generating a bit line select voltage having a magnitude based on the operational variance, the magnitude less than the unselect voltage so that the application of the bit line select voltage to an input terminal of a bit line selector receiving the select voltage causes the bit line selector to conduct, and the application of the bit line select voltage to an input terminal of a bit line selector receiving the unselect voltage biases the bit line selector off.
13. The method of claim 12 , wherein:
determining a operational variance associated with generating the unselect voltage comprises:
determining a leakage current generated during the generation of the unselect voltage.
14. The method of claim 13 , wherein:
generating a bit line select voltage comprises:
generating a bias signal based on the leakage current determined; and
generating the bit line select voltage based on the bias signal.
15. The method of claim 13 , wherein:
generating an unselect voltage comprises:
applying a first voltage to an input of a column selector;
applying a precharge voltage to a first terminal of the column selector; and
outputting the unselect voltage at a second terminal of the column selector.
16. A memory device, comprising:
a reference column selector configured to be connected to a precharge voltage;
a bias circuit connected to the reference column selector and configured bias an output of the reference column selector at a magnitude that is less than an unselect voltage so that application of an output of a column selector to a gate of a bit line transistor receiving a select voltage causes the bit line transistor to conduct.
17. The memory device of claim 16 , wherein:
the select voltage is generated from a ground voltage;
the unselect voltage is generated from a power supply voltage; and
the unselect voltage is equal to the power supply voltage minus a column selector voltage.
18. The memory device of claim 16 , wherein:
the column selector voltage comprises a leakage current voltage drop.
19. The memory device of claim 16 , wherein:
the bias circuit generates the bias signal based on a leakage current of a column selector outputting an unselect voltage to a bit line.
20. The memory device of claim 16 , wherein:
the bias circuit comprise a current source.
21. The memory device of claim 16 , further comprising:
a plurality of memory strings connected to the plurality of bit line selector transistors, each memory string defined by a plurality of memory cells.
22. The memory device of claim 15 , wherein:
the memory device comprises a flash memory device.
23. A memory device, comprising:
means for generating a select voltage and an unselect voltage; and
means for generating a gate voltage that causes a bit line selector transistor receiving the gate voltage at a gate and receiving the select voltage at a source to saturate, and that causes a bit line selector transistor receiving the gate voltage at a gate and receiving the unselect voltage at a source to be biased off.