Memory Device Reference Voltage Adjustment for Read Reliability
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Solution Overview
Problem
Existing memory devices face reliability issues during read operations due to unintentional changes in memory cell states caused by factors like temperature and stuck bits, leading to errors when using a single reference voltage for comparison.
Innovation Solution
The memory device dynamically adjusts the reference voltage based on the quantity of bits and detected errors during a read operation, performing multiple read operations with varying reference voltages to ensure accurate data retrieval.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single reference voltage is used for read operations, then the device complexity is reduced and operation is simplified, but the reliability deteriorates due to unintentional changes in memory cell states caused by temperature and stuck bits
Solution Approach 1:
The patent implements dynamic reference voltage adjustment by performing multiple read operations with different reference voltages (first read operation with first reference voltage, second read operation with second reference voltage) rather than using a fixed reference voltage. This dynamic approach adapts to changing memory cell states caused by temperature variations and stuck bits, thereby improving read operation reliability while managing the complexity through systematic voltage variation.
Solution Approach 2:
The patent changes the reference voltage parameter between read operations to compensate for unintentional changes in memory cell states. By varying the reference voltage (first reference voltage vs. second reference voltage) based on detected errors and quantity of bits, the system maintains accurate read operations despite environmental variations and memory cell degradation.
2Measurement precision
If multiple read operations with varying reference voltages are performed, then the reliability and data accuracy are improved, but the loss of time increases due to additional read operations
Solution Approach 1:
The patent uses feedback from the first read operation to determine whether to perform a second read operation. By detecting errors in the first read operation and comparing the quantity of bits to expected values, the system decides whether additional read operations with different reference voltages are necessary. This feedback mechanism ensures high data retrieval accuracy while minimizing unnecessary read operations that would increase time loss.
Solution Approach 2:
The patent performs a second read operation only when needed, based on the results of the first read operation and error detection. Rather than always performing multiple read operations, the system applies partial action by conditionally executing the second read operation only when errors are detected or the quantity of bits suggests potential issues, thereby balancing accuracy with time efficiency.
3Reliability
If the reference voltage is dynamically adjusted based on detected errors, then the reliability is improved by adapting to memory cell state changes, but the device complexity increases due to error detection and voltage adjustment mechanisms
Solution Approach 1:
The patent implements a self-service mechanism where the memory device automatically detects errors in read operations and adjusts the reference voltage accordingly without requiring external intervention. The system monitors the quantity of bits detected, compares it to expected values, and autonomously determines when to perform additional read operations with different reference voltages, thereby improving reliability while managing control complexity through automation.
Solution Approach 2:
The patent uses feedback from error detection mechanisms to dynamically adjust the reference voltage. By monitoring read operation results and comparing detected bit quantities to expected values, the system automatically modifies the reference voltage (switching between first and second reference voltages) to compensate for memory cell state changes, improving reliability through adaptive control.
Data Source
AI summary
Methods, systems, and devices for method for setting a reference voltage for read operations are described. A memory device may perform a first read operation on a set of memory cells using a first reference voltage and detect a first codeword based on performing the first read operation using the first reference voltage. The memory device may compare a first quantity of bits of the first codeword having a first logic value (e.g., a logic value ‘1’) with an expected quantity of bits having the first logic value (e.g., the expected quantity of logic value ‘1’s stored by the set of memory cells). The memory device may determine whether to perform a second read operation on the set of memory cells using a second reference voltage different than the first reference voltage (e.g., greater or less than the first reference voltage) based on the comparing.