FAQs and Answers about Read Disturb Phenomena
No matter how robust a data storage solution is, it will eventually succumb to the effects of degradation over time. It is often thought that data loss is primarily a problem with applications involving high levels of read/write cycles. However, read disturb phenomena are also a significant concern for engineers and OEMs.
What are read disturb errors?
NAND flash memory has been embraced by designers as a robust storage solution. However, OEMs have noticed a troublesome trend. As storage capability increases, reliability can sometimes decrease. This is largely due to read disturb phenomena. Read disturb errors occur in the absence of write capabilities. As data lines are repeatedly read, these cycles can have a wearing effect that can lead to data loss.
Which applications commonly encounter read disturb errors?
Read disturb errors can occur in any application in which write functions are not applicable. In other words, any application that is read-only may encounter read disturb errors. One common example of this is found in the gaming industry. Game developers write the data to the card once and then make the data read-only. Users who play the game do not write additional data to the card, but they access or read the data repeatedly. Although gaming is one of the most common examples, errors can occur in any type of application that prohibits any additional input from the users.
What is the role of a high voltage bias?
A biasing condition is one of the main causes of read disturb phenomena. Memory cells are arranged in long strings in a NAND flash array. This has the effect of working similarly to a multi-input NAND gate. When a read operation is activated, the selected data line is biased to a read threshold voltage. The unselected data lines are biased to a high voltage level, meaning that all cells on the NAND string are conducting. However, the cells of the unselected data lines have a tendency to become slightly programmed. With repeated activations of these particular read biasing configurations, those cells in the unselected data lines will acquire a programmed state. This is what causes a read disturb error.
Has your team been encountering unacceptable levels of read disturb phenomena in your flash storage? Contact the team at Delkin today to discuss alternative solutions. Our company offers custom storage solutions to meet the needs of a competitive marketplace.
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