US 9,812,213 B2
Flash memory, flash memory system and operating method of the same
Kyung-Ryun Kim, Daejeon (KR); and Sang-Yong Yoon, Seoul (KR)
Assigned to SAMSUNG ELECTRONICS CO., LTD., Suwon-si, Gyeonggi-Do (KR)
Filed by SAMSUNG ELECTRONICS CO., LTD., Suwon-si, Gyeonggi-do (KR)
Filed on Apr. 14, 2016, as Appl. No. 15/98,791.
Application 15/098,791 is a continuation of application No. 14/150,320, filed on Jan. 8, 2014, granted, now 9,330,775.
Claims priority of application No. 10-2013-0004037 (KR), filed on Jan. 14, 2013.
Prior Publication US 2016/0225458 A1, Aug. 4, 2016
Int. Cl. G11C 16/28 (2006.01); G11C 11/56 (2006.01); G11C 16/04 (2006.01)
CPC G11C 16/28 (2013.01) [G11C 11/5642 (2013.01); G11C 16/0483 (2013.01)] 19 Claims
OG exemplary drawing
 
1. A method of operating a flash memory comprising a plurality of memory cells, the method comprising:
defining a first adjacent threshold voltage range and a second adjacent threshold voltage range for a first pair of threshold voltage distributions adjacently located;
counting the number of memory cells having threshold voltages included in the first adjacent threshold voltage range by subtracting the number of the memory cells having a threshold voltage lower than a first search read voltage from a number of the memory cells having a threshold voltage lower than a first reference read voltage;
counting the number of memory cells included in the second adjacent threshold voltage range by subtracting the number of the memory cells having a threshold voltage lower than the first reference read voltage from the number of the memory cells having a threshold voltage lower than a second search read voltage; and
setting a first optimal read voltage based on a count difference between the counted number of the memory cells having the threshold voltages included in the first adjacent threshold voltage range and the counted number of the memory cells having the threshold voltages included in the second adjacent threshold voltage range,
wherein setting the first optimal read voltage based on the count difference, is performed by calculating using a result value generated from applying a first adjustment parameter to the count difference, wherein the first adjustment parameter is a slope of a tangent at the origin of a graph representing the count difference verses a threshold voltage of the memory cells.