# US 2017/0365307 A1 · Data storage device and operating method thereof > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2017/0365307 A1 - Document ID: US20170365307A1 - Status: Published application - Kind: A1 - Application number: 15/265,949 - Filed: 2016-09-15 - Published: 2017-12-21 - Earliest claimed: 2016-06-20 - Assignees: SK hynix Inc. - Applicants: SK hynix Inc. - Inventors: Myeong Woon JEON - Web page: https://patentgrep.com/patent/US20170365307A1 ## CPC - G11C 11/5642: {Sensing or reading circuits; Data output circuits} - G11C 16/28: using differential sensing or reference cells, e.g. dummy cells - G11C 16/30: Power supply circuits - G11C 2211/5634: Reference cells - G11C: STATIC STORES (semiconductor memory devices H10B) ## Abstract A method for operating a data storage device includes determining appropriateness of a first read bias for adjacent target threshold voltage distributions among threshold voltage distributions for a plurality of memory cells; and if it is determined that the first read bias is inappropriate, determining a second read bias. ## Claims ### Claim 1 A method for operating a data storage device, comprising: determining appropriateness of a first read bias for adjacent target threshold voltage distributions among threshold voltage distributions for a plurality of memory cells; and if it is determined that the first read bias is inappropriate, determining a second read bias. ### Claim 2 (depends on 1) The method according to claim 1, wherein the determining of the appropriateness of the first read bias comprises: determining a number of memory cells which have threshold voltages lower than the first read bias, among the plurality of memory cells; and determining the appropriateness of the first read bias based on the number of memory cells and a reference number corresponding to the target threshold voltage distributions. ### Claim 3 (depends on 2) The method according to claim 2, wherein the determining of the number of memory cells comprises: obtaining data read from the memory cells based on the first read bias; and determining a number of bits having a predetermined value, included in the data. ### Claim 4 (depends on 1) The method according to claim 1, wherein the determining of the second read bias comprises: determining the second read bias based on a gradient decent algorithm. ### Claim 5 (depends on 1) The method according to claim 1, wherein the determining of the second read bias comprises: determining an average threshold voltage of a first target threshold voltage distribution of the target threshold voltage distributions, based on a Gaussian distribution function; and determining the second read bias based on the average threshold voltage and an estimated width of the first target threshold voltage distribution. ### Claim 6 (depends on 5) The method according to claim 5, wherein the determining of the average threshold voltage comprises: determining the average threshold voltage by determining an area rate of a partial distribution formed by the first read bias in the first target threshold voltage distribution and applying the area rate to an integral equation for the Gaussian distribution function. ### Claim 7 (depends on 5) The method according to claim 5, wherein the determining of the average threshold voltage comprises: determining the average threshold voltage by determining an area rate of a partial distribution formed by the first read bias in the first target threshold voltage distribution and applying the area rate to an inverse function of a Q function. ### Claim 8 A method for operating a data storage device, comprising: determining appropriateness of a first read bias for adjacent target threshold voltage distributions among threshold voltage distributions for a plurality of memory cells; if it is determined that the first read bias is inappropriate, determining a start bias corresponding to the target threshold voltage distributions, based on a Gaussian modeling algorithm and an error rate of the first read bias; and determining a second read bias based on the start bias. ### Claim 9 (depends on 8) The method according to claim 8, wherein the determining of the appropriateness of the first read bias comprises: determining a number of memory cells which have threshold voltages lower than the first read bias, among the plurality of memory cells; and determining the appropriateness of the first read bias based on the number of memory cells and a reference number corresponding to the target threshold voltage distributions. ### Claim 10 (depends on 9) The method according to claim 9, wherein the determining of the number of memory cells comprises: obtaining data read from the memory cells based on the first read bias; and determining a number of bits having a predetermined value, Included in the data. ### Claim 11 (depends on 8) The method according to claim 8, wherein the determining of the start bias comprises: determining an average threshold voltage of a first target threshold voltage distribution of the target threshold voltage distributions, based on a Gaussian distribution function and the error rate; and determining the start bias based on the average threshold voltage and an estimated width of the first target threshold voltage distribution. ### Claim 12 (depends on 11) The method according to claim 11, wherein the determining of the average threshold voltage comprises: determining the average threshold voltage by applying the error rate to an integral equation for the Gaussian distribution function. ### Claim 13 (depends on 11) The method according to claim 11, wherein the determining of the average threshold voltage comprises: determining the average threshold voltage by applying the error rate to an inverse function of a Q function. ### Claim 14 (depends on 8) The method according to claim 8, wherein the determining of the second read bias comprises: determining the second read bias by estimating a gradient of a target threshold voltage distribution in which the start bias is positioned, based on a gradient decent algorithm. ### Claim 15 (depends on 8) The method according to claim 8, wherein the determining of the second read bias comprises: determining the start bias as the second read bias. ### Claim 16 A method for operating a data storage device, comprising: determining a start bias corresponding to adjacent target threshold voltage distributions among threshold voltage distributions of a plurality of memory cells, based on a Gaussian modeling algorithm and a first read bias; and determining a second read bias for the target threshold voltage distributions, based on the start bias. ### Claim 17 (depends on 16) The method according to claim 16, wherein the determining of the start bias comprises: determining an average threshold voltage of a first target threshold voltage distribution of the target threshold voltage distributions, based on a Gaussian distribution function; and determining the start bias based on the average threshold voltage and an estimated width of the first target threshold voltage distribution. ### Claim 18 (depends on 17) The method according to claim 17, wherein the determining of the average threshold voltage comprises: determining the average threshold voltage by determining an error rate of the first read bias for the target threshold voltage distributions and applying the error rate to an integral equation for the Gaussian distribution function. ### Claim 19 (depends on 17) The method according to claim 17, wherein the determining of the average threshold voltage comprises: determining the average threshold voltage by calculating an error rate of the first read bias for the target threshold voltage distributions and applying the error rate to an inverse function of a Q function. ### Claim 20 (depends on 16) The method according to claim 16, wherein the determining of the second read bias comprises: determining the second read bias by estimating a gradient of a target threshold voltage distribution in which the start bias is positioned, based on a gradient decent algorithm.