Column Decoder Driving Voltage Control for Low Power DRAM
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Solution Overview
Problem
Conventional semiconductor memory apparatuses face high power consumption due to large leakage currents in column decoders, particularly in drivers producing column select signals, which occupy significant area and affect yield in low power mobile DRAMs.
Innovation Solution
A column decoder with a driving voltage input node that uses a controllable driving voltage, isolated from external voltage VDD, is implemented to reduce leakage current by incorporating a driving voltage supply controller that manages power supply based on specific operating modes, such as precharge power down standby or self refresh modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional drivers using external voltage VDD and ground voltage VSS are used to produce column select signals, then the drivers can reliably produce the required column select signals, but the drivers occupy significant area and generate large leakage current
Solution Approach 1:
The driver circuit is divided into two separate circuits: a first driver circuit using external voltage VDD for normal operation, and a second driver circuit using internal voltage VDD_INT for power-down mode. This segmentation allows each circuit to be optimized for its specific operating condition, reducing overall area while maintaining reliability.
Solution Approach 2:
The patent dynamically switches between two driver circuits based on the operating mode. During power-down mode, the second driver circuit using internal voltage is activated to reduce leakage current and area occupancy, while the first driver circuit handles normal operation. This dynamic adaptation resolves the contradiction between reliability and area efficiency.
2Power
If conventional drivers using external voltage VDD and ground voltage VSS are used to produce column select signals, then the drivers can produce sufficient driving strength, but the leakage current becomes substantial (20% of entire IDD 2P value)
Solution Approach 1:
The driver functionality is segmented into two separate driver circuits, each optimized for specific operating conditions. The first driver circuit handles normal operation with adequate driving strength, while the second driver circuit activates during power-down mode to minimize leakage current, thus resolving the contradiction between driving strength and energy loss.
Solution Approach 2:
The patent changes the voltage parameter from external VDD to internal VDD_INT during power-down mode. This parameter change reduces the leakage current significantly while maintaining sufficient driving strength for the intended operation, thereby reducing energy loss without completely sacrificing driving capability.
3Adaptability or versatility
If drivers are disposed in an array structure to produce all column select signals YI, then all column select signals can be produced, but the total area occupied by drivers becomes significant
Solution Approach 1:
The array of drivers is segmented into two functional groups: first driver circuits for normal operation and second driver circuits for power-down mode. This segmentation allows the system to use only the necessary driver circuits for each operating mode, reducing the effective area occupied while maintaining full column select signal coverage capability.
Solution Approach 2:
The second driver circuits using internal voltage VDD_INT serve multiple functions: they provide column select signals during power-down mode and can potentially serve as backup or alternative drivers during normal operation. This multi-functionality reduces the need for dedicated drivers for every scenario, thereby reducing total area occupancy.
Data Source
AI summary
The present invention relates to a column decoder for low power consumption in a semiconductor memory apparatus. The semiconductor device according to the present invention includes a column select signal decoder, which has a driving voltage input node and uses a driving voltage, for producing a plurality of column select signals by decoding a column select control signal; and a driving voltage supply controller for controlling a supply of the driving voltage to the driving voltage input node.