Apparatus and method for determining an operating condition of a memory cell based on cycle information
A method populates a parameter set for dynamically adjusting an operating condition in a memory block of a non-volatile memory circuit. A desired condition limit is identified, and a first parameter is computed as a function of a first memory operation to be performed on the memory block. The first parameter is included in a parameter set, and the memory block is cycled until the operating condition reaches the desired condition limit. After cycling, a second parameter is determined as a function of a second memory operation to be performed on the memory block, and the second parameter is included in the parameter set. The steps of cycling, and determining and the including the second parameter may be repeated until a desired number of cycles/parameters are reached. A retention bake may also be performed on the memory circuit, and a bit error rate resulting from a read operation verified.
1. A method for populating a parameter set for dynamically adjusting an operating condition in a memory block of a non-volatile memory circuit, comprising:
identifying a desired condition limit;
computing a first parameter as a function of a first memory operation to be performed on the memory block, the operating condition being a function of the parameter;
including the first parameter in the parameter set;
cycling the memory block until the operating condition reaches the desired condition limit;
determining after the cycling a second parameter as a function of a second memory operation to be performed on the memory block;
including the second parameter in the parameter set;
repeating the cycling and the determining and the including the second parameter steps until a desired number of cycles is reached;
performing a retention bake on the memory circuit;
performing a read operation on the memory block; and
verifying a bit error rate resulting from the read operation does not exceed a desired error rate.
2. The method of claim 1 , wherein the first and second memory operations are programming operations, the operating condition is a programming time, and the condition limit is a minimum programming duration.
3. The method of claim 1 , wherein the first and second memory operations are programming operations, the operating condition is an erase time, and the condition limit is a maximum erase duration.
4. The method of claim 1 , wherein the first and second memory operations are programming operations, the operating condition is a voltage threshold distribution in the memory block, and the condition limit is a maximum distribution width.
5. The method of claim 1 , wherein the first parameter and second parameter are one of a starting pulse magnitude, incremental step pulse magnitude, and pulse width.
6. The method of claim 5 , wherein the first and second parameters are associated with an incremental step pulse program operation.
7. The method of claim 5 , wherein the first and second parameters are associated with an incremental step pulse erase operation.
8. The method of claim 1 , further comprising:
storing the parameter set in a lookup table, the first and second parameters each being indexed in the lookup table by a respective number or range of program/erase cycles.
9. A method for populating a parameter set for flash memory operations, comprising:
determining one or more first parameters for a type of memory operation based on one or more predetermined operating conditions;
cycling one or more memory blocks, using the one or more first parameters, for a predetermined number of cycles;
determining, after the cycling, one or more new parameters for the type of memory operation based on one or more current characteristics;
performing a read operation on the one or more memory blocks; and
verifying that a bit error rate resulting from the read operation does not exceed a predetermined error rate; and
storing, based on the bit error rate not exceeding the predetermined error rate, the one or more new parameters in connection with a cycle index for retrieving the stored parameters in connection with a memory operation of the type based on the cycle index.
10. The method of claim 9 , further comprising:
performing a retention bake on the one or more memory blocks.
11. The method of claim 9 , wherein the one or more first parameters and the one or more new parameters comprise one or more of a starting pulse magnitude, incremental step pulse magnitude, and pulse width.
12. The method of claim 9 , wherein a respective cycle of the predetermined number of cycles comprises a program operation and an erase operation.
13. The method of claim 9 , wherein the one or more current circuit characteristics comprises one or more of a current bit error rate, current memory cell program time, and current memory cell erase time.
14. The method of claim 9 , wherein the memory operation is an erase operation.
15. The method of claim 9 , wherein the memory operation is a program operation.
16. The method of claim 15 , wherein the one or more first parameters and the one or more new parameters are associated with an incremental step pulse program operation.
17. The method of claim 9 , wherein determining the one or more new parameters comprises:
selecting one or more respective parameters that, when used in connection with a subsequent memory operation, achieve the one or more predetermined operating conditions.
18. The method of claim 9 , wherein the one or more predetermined operating conditions comprises a predetermined memory cell program time or a predetermined memory cell erase time.
19. The method of claim 9 , wherein storing the one or more new parameters comprises storing the one or more new parameters in a lookup table, the lookup table configured to be accessed by a memory controller for memory operations performed on the one or more memory blocks, and wherein the cycle index is indexable by a number or range of cycles.
20. A method for populating a parameter set for flash memory operations, comprising:
cycling one or more memory blocks for a predetermined number of cycles, using erase and program operations in connection with one or more predetermined parameters;
determining, after the cycling, one or more new parameter values for the one or more predetermined parameters in subsequent erase and program operations based on a current erase time or program time;
performing, after the determining, one or more program and erase cycles on the one or more memory blocks;
executing, after the performing, a read operation on the one or more memory blocks;
verifying that a bit error rate resulting from the read operation does not exceed a predetermined error rate; and
storing the one or more new parameters in a lookup table associated with a memory controller of a solid-state drive, the lookup table being indexed by the predetermined number of cycles for retrieval of the one or more new parameter values by the memory controller during operation of the solid-state drive.