Sense Amplifier Voltage Control for DRAM Current Reduction
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Solution Overview
Problem
In semiconductor devices like DRAM, the continuous supply of operation voltage to the common source during the active period leads to increased consumption current due to leak current, and attempts to equalize the sense amplifier during this period risk losing information stored in memory cells if the equalization period is long.
Innovation Solution
The implementation of a driver circuit that adjusts the operation voltage of the common source lines during the active and power down modes, using a second driver circuit to reduce off-leak current and prevent information loss by applying a lower voltage to the bit lines during power down, and ensuring data integrity through controlled voltage changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If operation voltage is continuously supplied to the common source during the active period, then the sense amplifier can maintain readiness for read/write operations, but consumption current increases due to leak current flowing through the sense amplifier
Solution Approach 1:
The patent applies periodic action by alternating between two voltage supply states: supplying operation voltage to the common source only when read/write operations are needed, and stopping the supply during periods when no operations are performed. This periodic switching resolves the contradiction by eliminating continuous energy loss while maintaining operational readiness when required.
Solution Approach 2:
The patent implements preliminary action by pre-charging the bit lines to a predetermined potential before operation voltage is supplied to the common source. This preliminary preparation ensures that when the sense amplifier becomes active, the bit lines are already ready for immediate read/write operations, eliminating the need to maintain continuous voltage supply for bit line charging.
2Loss of energy
If the sense amplifier is equalized during the active period to reduce leak current, then consumption current decreases, but information held in the memory cell may be lost when the equalizing period is long
Solution Approach 1:
The patent applies local quality by differentiating the treatment of different circuit components during the active period. The common source voltage is stopped to reduce leak current, while the bit lines maintain their charge through preliminary pre-charging. This localized differentiation allows current reduction without affecting information storage in the memory cells.
Solution Approach 2:
The patent uses preliminary action by pre-charging the bit lines before stopping the common source voltage supply. This preliminary charging ensures that the bit lines maintain their potential and can continue to hold information even when the common source is equalized, thus preventing information loss while enabling current reduction.
Data Source
AI summary
An apparatus includes a memory cell, a bit line coupled to the memory cell, and a sense amplifier configured to amplify a data signal on the bit line read out from the memory cell. The sense amplifier is operated in a first mode with a first power source voltage difference and operated in a second mode with a second power source voltage difference smaller than the first power source voltage difference.