Updating read voltages using syndrome weight comparisons

Patent metadata

Field	Value
Publication number	US-9697905-B2
Application number	US-201414561084-A
Country	US
Kind code	B2
Filing date	Dec 4, 2014
Priority date	May 31, 2013
Publication date	Jul 4, 2017
Grant date	Jul 4, 2017

Abstract

A method performed at a data storage device includes adjusting a first read voltage and a second read voltage to form sets of read voltages. First representations of data are read from a logical page in the non-volatile memory according to the sets of read voltages. The first representations of the data correspond to multiple values of the first read voltage and the second read voltage. The first representations of the data are stored in a memory and second representations of the data are generated based on the first representations. A value of the first read voltage is selected based on syndrome weights corresponding to the second representations.

First claim

What is claimed is:

1. A method of updating a set of read voltages, the method comprising:
in a data storage device including a controller and a non-volatile memory, performing:
iteratively adjusting a first read voltage and a second read voltage to form sets of read voltages, wherein each of the sets of read voltages includes a first value of the first read voltage and a second value of the second read voltage, wherein an adjustment of the second read voltage is a function of an adjustment of the first read voltage;
reading first representations of data from a logical page in the non-volatile memory according to the sets of read voltages, the first representations of the data corresponding to multiple values of the first read voltage and the second read voltage;
storing the first representations of the data in a memory and converting the first representations of the data from a first mapping of threshold voltage ranges to bit sequences to a second mapping that includes fewer bits per bit sequence than the first mapping;
generating second representations of the data based on the first representations, the second representations corresponding to adjusting the first read voltage and the second read voltage; and
selecting a value of the first read voltage based on a comparison of syndrome weights corresponding to the second representations.

2. The method of claim 1 , wherein iteratively adjusting the first read voltage and the second read voltage to form the sets of read voltages includes:
forming a first set of read voltages that includes an initial value of the first read voltage and that includes an initial value of the second read voltage;
applying a first offset to the initial value of the first read voltage to generate a first adjusted value of the first read voltage;
applying a second offset to the initial value of the second read voltage to generate a first adjusted value of the second read voltage; and
forming a second set of read voltages that includes the first adjusted value of the first read voltage and the first adjusted value of the second read voltage.

3. The method of claim 1 , wherein reading the first representations of the data from the logical page according to the sets of read voltages includes:
generating a first representation of the data according to a first set of read voltages by:
sensing a group of storage elements using the first value of the first read voltage of the first set of read voltages to generate first sensing data;
sensing the group of storage elements using the second value of the second read voltage of the first set of read voltages to generate second sensing data; and
performing a logical operation on the first sensing data and the second sensing data to generate the first representation of the data; and

generating a second representation of the data according to a second set of read voltages by:
sensing the group of storage elements using the first value of the first read voltage of the second set of read voltages to generate third sensing data;
sensing the group of storage elements using the second value of the second read voltage of the second set of read voltages to generate fourth sensing data; and
performing a logical operation on the third sensing data and the fourth sensing data to generate the second representation of the data.

4. The method of claim 1 , wherein generating the second representations of the data includes:
generating a first trial value of the data corresponding to the first read voltage having a first voltage value and the second read voltage having a second voltage value; and
generating a second trial value of the data corresponding to the first read voltage having a third voltage value and the second read voltage having the second voltage value; and
wherein selecting the value of the first read voltage includes:
inputting the first trial value of the data to an ECC decoder;
receiving a first syndrome weight from the ECC decoder, the first syndrome weight associated with a first number of errors corresponding to the first trial value of the data;
inputting the second trial value of the data to the ECC decoder;
receiving a second syndrome weight from the ECC decoder, the second syndrome weight associated with a second number of errors corresponding to the second trial value of the data; and
selecting the value of the first read voltage to be the first voltage value in response to the first syndrome weight being a lowest of the syndrome weights or selecting the value of the first read voltage to be the third voltage value in response to the second syndrome weight being the lowest of the syndrome weights.

5. The method of claim 4 , wherein the syndrome weights form a first set of syndrome weights, wherein each syndrome weight of the first set of syndrome weights is associated with a corresponding adjusted value of the first read voltage and is based on the second representations of the data, the method further comprising:
generating a first interpolated syndrome weight based on the first set of syndrome weights; and
selecting a value of the first read voltage based on a voltage associated with the first interpolated syndrome weight.

6. The method of claim 5 , wherein generating the first interpolated syndrome weight includes upsampling the first set of syndrome weights to generate upsampled data, applying a low-pass filter to the upsampled data to generate interpolation data, and locating a smallest interpolation data value in the interpolation data, wherein the smallest interpolation data value is a value in the interpolation data that is smaller than any other value in the interpolation data and that is located by a peak detector operating on the interpolation data.

7. The method of claim 5 , further comprising selecting an interpolation filter from a set of multiple interpolation filters based on the first set of syndrome weights by selecting a first interpolation filter from the set of multiple interpolation filters in response to the first set of syndrome weights matching a first pattern of syndrome weights or selecting a second interpolation filter from the set of multiple interpolation filters in response to the first set of syndrome weights not matching the first pattern of syndrome weights.

8. A data storage device comprising:
a non-volatile memory; and
a controller coupled to the non-volatile memory, wherein the controller is configured to adjust a first read voltage and a second read voltage to form sets of read voltages, wherein each of the sets of read voltages includes a first value of the first read voltage and a second value of the second read voltage, wherein the controller is configured to store first representations of the data into a memory, the first representations read from a logical page in the non-volatile memory according to the sets of read voltages, the first representations of the data corresponding to multiple values of the first read voltage and the second read voltage,
wherein the controller is further configured to generate second representations of the data based on the first representations, the second representations corresponding to adjusting the first read voltage and the second read voltage, and wherein the controller is configured to select a value of the first read voltage based on a voltage associated with a first interpolated syndrome weight that is based on syndrome weights corresponding to the second representations.

9. The data storage device of claim 8 , wherein the controller is configured to convert the first representations of the data in the memory from a first mapping of threshold voltage ranges to bit sequences to a second mapping that includes fewer bits per bit sequence than the first

Assignees

• Sandisk Technologies Inc
• Sandisk Technologies Llc

Inventors

• Sharon Eran
• Navon Ariel
• Bazarsky Alexander

Classifications

• G06F11/004

  Error avoidance (G06F11/07 and subgroups take precedence) · CPC title

• G11C2029/0411

  Online error correction · CPC title

• G11C16/349

  Arrangements for evaluating degradation, retention or wearout, e.g. by counting erase cycles · CPC title

• G06F11/1048

  using arrangements adapted for a specific error detection or correction feature · CPC title

• G11C7/14

  Dummy cell management; Sense reference voltage generators · CPC title