DRAM Wordline Driver Dual-Voltage Charging Circuit
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Solution Overview
Problem
The power consumption of wordline drivers in DRAM is high due to low driving efficiency of VPP charge pumps, which is challenging to reduce without adding significant hardware resources.
Innovation Solution
A wordline driver design utilizing a multiplexer configuration with two transistors and a voltage multiplexer, allowing the use of a lower voltage (VEXT) for initial charging and switching to a higher voltage (VPP) for faster charging, thereby optimizing power usage by distributing current from both voltages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If VPP charge pump is used to generate voltage VPP for charging the wordline, then the wordline can be charged to the required voltage level, but the power consumption is high due to low driving efficiency
Solution Approach 1:
The charging process is segmented into two phases: initial charging from VNWL to an intermediate voltage level using VEXT, and subsequent charging from the intermediate level to VPP using the charge pump. This segmentation allows the system to use the more efficient VEXT for the bulk of the charging work, reducing overall power consumption while maintaining the required final voltage level.
Solution Approach 2:
The invention changes the voltage parameter strategy by introducing a dual-voltage approach (VEXT and VPP) instead of relying solely on VPP. By dynamically switching between different voltage sources based on the charging stage, the system optimizes power consumption while maintaining charging effectiveness.
2Device complexity
If only VPP is used for charging the wordline, then the charging process is simple, but the power consumption cannot be reduced
Solution Approach 1:
The multiplexer circuit serves multiple functions: it selects between VEXT and VPP voltage sources, controls the charging stages, and manages the switching between different transistor pairs. This multi-functionality allows the added complexity to be justified by the significant power consumption reduction achieved through dual-voltage operation.
3Power
If VEXT is used for initial charging and VPP for subsequent charging, then power consumption is reduced, but the circuit complexity increases due to multiplexer and additional transistors
Solution Approach 1:
The circuit employs dynamic switching between VEXT and VPP based on real-time charging conditions. The multiplexer and control logic continuously monitor the wordline voltage and automatically transition between voltage sources, making the circuit adaptive rather than static. This dynamic behavior optimizes power consumption throughout the charging process.
Solution Approach 2:
The multiplexer acts as an intermediary component that mediates between the two voltage sources (VEXT and VPP) and the wordline. It intelligently selects which voltage source to connect based on the charging stage, adding controlled complexity that enables the power consumption reduction strategy to function properly.
Data Source
AI summary
A wordline driver for DRAM comprises a multiplexer, an inverter and a transistor switch. One end of the multiplexer is connected to a wordline charging voltage, and the other end is connected to an external voltage, wherein the external voltage is less than the wordline charging voltage, and initially the external voltage is outputted. The output end of the inverter is connected to the select line of the multiplexer, and the input end thereof is electrically connected to the output end of the multiplexer. One end of the transistor switch is connected to the input end of the inverter, and the other end thereof is connected to the word line.