Read Pass Voltage Discharge Staging for Peak Icc Reduction
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Solution Overview
Problem
The challenge of managing peak current consumption (Icc) during read operations in semiconductor memory systems, particularly in 3D memory structures with a high number of word lines, which can exceed specified limits and lead to operation failures due to voltage drops.
Innovation Solution
Implementing a multi-stage discharge of the read pass voltage (Vread) during read operations, reducing it to intermediate and final voltages in stages, along with adjusting the read reference voltage, to manage peak current consumption effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a high number of word lines are used in 3D memory structures to increase storage capacity, then bit density is improved, but peak current consumption during read operations exceeds specified limits
Solution Approach 1:
The read pass voltage discharge process is segmented into multiple stages: an initial rapid discharge phase followed by a slower discharge phase. This segmentation allows the system to quickly reduce voltage during the critical early read period when current consumption is most problematic, then gradually discharge remaining voltage to maintain stability without excessively prolonging read operations.
Solution Approach 2:
The discharge rate of the read pass voltage is made dynamic rather than static. The system transitions from a fast discharge mode at the beginning of the read operation to a slower discharge mode as the operation progresses. This dynamic adjustment optimizes current consumption at different phases of the read cycle while maintaining overall read performance.
2Use of energy by moving object
If the read pass voltage is discharged rapidly to reduce peak current, then current consumption is reduced, but read operation time may be prolonged
Solution Approach 1:
The voltage discharge is segmented into two distinct phases: a first phase with rapid discharge to quickly reduce peak current consumption, and a second phase with slower discharge to complete the voltage reduction without excessively extending the read operation. This time-segmented approach balances current reduction with read speed maintenance.
Solution Approach 2:
The discharge rate parameter is changed over time during the read operation. Initially, a high discharge rate is applied to reduce peak current, then the discharge rate parameter is adjusted to a lower value to complete the discharge process efficiently. This parameter transformation allows optimization of both current consumption and read time.
3Use of energy by moving object
If the read pass voltage is reduced to manage peak current, then current profiles become uniform, but the effectiveness of unselected memory cell turning on may be compromised
Solution Approach 1:
The read pass voltage is applied at full strength at the beginning of the read operation to ensure all unselected memory cells are reliably turned on before sensing begins. This preliminary high-voltage action guarantees proper cell activation, after which the voltage discharge process begins to manage current consumption for the remainder of the operation.
Solution Approach 2:
The read operation uses periodic voltage levels: an initial high read pass voltage to activate unselected cells, followed by a controlled discharge to a lower voltage level. This periodic voltage application ensures reliable cell operation during the critical sensing window while managing current consumption during the subsequent period.
Data Source
AI summary
Technology is disclosed herein for a storage system and method for multi-stage discharge of a read pass voltage. In an aspect, the voltage on unselected word lines is reduced from the read pass voltage to an intermediate voltage during a first stage near the end of a read operation. A read reference voltage on the selected word line may be changed (e.g., increased) to the intermediate voltage during the first stage. During a second stage the voltage on the unselected word lines may be reduced from the intermediate voltage to a final voltage. The voltage on the selected word line may also be decreased during the second stage from the intermediate voltage to the final voltage. The multi-stage discharge of the read pass voltage may reduce peak current consumption (e.g., peak Icc) in a final portion of the read operation.