Table lookup voltage compensation for memory cells
View Patent ↗Systems and methods of regulating voltage at a memory cell are disclosed. An address for the memory cell is determined. Table lookups based on the address are performed. The table lookups yield voltage compensation parameters that can be used to set voltages on the terminals (e.g., source and drain) of the memory cell.
1. A computer-implemented voltage compensation method, said method comprising:
performing a first table lookup based on an address of a memory cell in an array of memory cells to select a first voltage compensation parameter;
performing a second table lookup based on said address to select a second voltage compensation parameter;
combining said first and second voltage compensation parameters and an uncompensated voltage value to determine a compensated voltage value; and
setting a voltage at a terminal of said memory cell to said compensated voltage value.
2. The method of claim 1 wherein said first voltage compensation parameter is a function of the location of said memory cell measured in a first dimension of said array and wherein said second voltage compensation parameter is a function of the location of said memory cell measured in a second dimension of said array.
3. The method of claim 1 wherein said terminal comprises a region selected from the group consisting of: a source region of said memory cell; a drain region of said memory cell.
4. The method of claim 1 further comprising performing a third table lookup based on said address to select a third voltage compensation parameter that is a function of distance between said memory cell and an electrical contact closest to said memory cell, and wherein said third voltage compensation parameter is combined with said first and second voltage compensation parameters and said uncompensated voltage value to determine said compensated voltage value.
5. The method of claim 4 wherein said terminal comprises a drain region of said memory cell.
6. The method of claim 1 further comprising:
encoding said compensated voltage value as a bit string; and
inputting said bit string to a voltage regulator that sets said voltage at said terminal to said compensated voltage value.
7. The method of claim 1 further comprising selecting a lookup table for said first table lookup and a lookup table for said second table lookup from a first set of lookup tables if said memory cell is soft programmed, wherein otherwise a lookup table for said first table lookup and a lookup table for said second table lookup are selected from a second set of lookup tables.
8. A system comprising:
a plurality of memory cells; and
a microcontroller coupled to said memory cells and operable for accessing at least one lookup table comprising a plurality of voltage compensation parameters; wherein said microcontroller is operable for performing a first table lookup that yields a first voltage compensation value that is selected from said plurality of voltage compensation parameters based on an address associated with a memory cell of said plurality of memory cells, and wherein said microcontroller is also operable for performing a second table lookup that yields a second voltage compensation value that is selected from said plurality of voltage compensation parameters based on said address, wherein a compensated voltage value that is based on both said first voltage compensation value and said second voltage compensation value is applied to a terminal of said memory cell.
9. The system of claim 8 wherein said first voltage compensation value is a function of the location of said memory cell measured in a first dimension and wherein said second voltage compensation value is a function of the location of said memory cell measured in a second dimension.
10. The system of claim 8 wherein said terminal comprises a region selected from the group consisting of: a source region of said memory cell; a drain region of said memory cell.
11. The system of claim 8 wherein said microcontroller is also operable for performing a third table lookup that yields a third voltage compensation value that is selected from said plurality of voltage compensation parameters based on said address, wherein said third voltage compensation value is a function of distance between said memory cell and an electrical contact closest to said memory cell, and wherein said compensated voltage value is based on said first voltage compensation value, said second voltage compensation value, and said third voltage compensation value.
12. The system of claim 11 wherein said terminal comprises a drain region of said memory cell.
13. The system of claim 8 wherein said microcontroller encodes said compensated voltage value as a bit string that is transmitted to a voltage regulator, wherein said voltage regulator comprises a digital-to-analog converter that supplies said compensated voltage value to said terminal.
14. The system of claim 8 wherein said first table lookup and said second table lookup are performed using a first plurality of lookup tables if said memory cell is soft programmed, wherein otherwise said first table lookup and said second table lookup are performed using a second plurality of lookup tables.
15. A computer-readable medium having stored thereon, computer-executable instructions that, responsive to execution by a computing device, cause the computing device to perform operations comprising:
identifying an address in said array that is associated with said memory cell;
selecting a first entry in a first lookup table, wherein said first entry corresponds to said address and wherein said first lookup table comprises first information useful for determining a first compensated voltage value for a drain of said memory cell;
selecting a second entry in a second lookup table, wherein said second entry corresponds to said address and wherein said second lookup table comprises second information useful for determining a second compensated voltage value for a source of said memory cell; and
setting a voltage at said drain to said first compensated voltage value and setting a voltage at said source to said second compensated voltage value.
16. The computer-readable medium of claim 15 wherein said first compensated voltage value and said second compensated voltage value are each a function of a two-dimensional location of said memory cell in said array.
17. The computer-readable medium of claim 16 wherein said first compensated voltage value is also a function of distance between said memory cell and an electrical contact closest to said memory cell.
18. The computer-readable medium of claim 15 wherein said operations further comprise updating entries in said first and second lookup tables such that values of said first and second entries are replaced with different values.
19. The computer-readable medium of claim 15 wherein said operations further comprise selecting said first and second lookup tables from a first set of lookup tables for soft programming of said memory cell, wherein otherwise said first and second lookup tables are selected from a second set of lookup tables.