DRAM Voltage Generator Fast Response via Segmented Control
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Solution Overview
Problem
Conventional DC voltage generators in DRAM systems with DDR4 standard have slow response times, which can be improved but at the cost of worsening power supply rejection ratio (PSRR) and stability when reducing capacitor capacitance.
Innovation Solution
Incorporating a controllable voltage divider with a pull-up circuit and a first and second pull-down circuit to selectively connect reference voltages, allowing for faster voltage level achievement without compromising PSRR and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If the capacitance of capacitors C1 and C2 is reduced to improve response time, then the response time is improved, but the power supply rejection ratio (PSRR) and stability are worsened
Solution Approach 1:
The patent divides the voltage adjustment function into two separate circuits: a first voltage adjustment circuit for coarse adjustment and a second voltage adjustment circuit for fine adjustment. This segmentation allows each circuit to be optimized independently - the first circuit can use larger capacitors for stability while the second circuit provides fast response through its own compensation capacitor, resolving the contradiction between response time and stability
Solution Approach 2:
The second voltage adjustment circuit acts as an intermediary that compensates for the slow response of the first voltage adjustment circuit. When voltage adjustment is needed, the second circuit quickly adjusts the voltage through its compensation capacitor Cf, while the first circuit maintains overall stability with its larger capacitors C1 and C2, thus mediating between speed and stability requirements
2Reliability
If conventional voltage generator design is used to maintain stability and PSRR, then stability and PSRR are maintained, but the response time is slow
Solution Approach 1:
The patent introduces dynamic control mechanisms where the second voltage adjustment circuit is selectively activated based on adjustment requirements. The control circuit determines when to engage the second circuit for fast response, making the system dynamically adaptive rather than statically optimized for a single performance metric, thus achieving both fast response and maintained stability
Data Source
AI summary
A voltage generator includes a controllable voltage divider, a pull-up circuit and a first pull-down circuit. The controllable voltage divider is utilized for generating an output voltage at an output node of the controllable voltage divider according to a first reference voltage, a second reference voltage, and a control signal, wherein the second reference voltage is lower than the first reference voltage. The pull-up circuit is coupled to the output node of the controllable voltage divider and the first reference voltage, and is utilized for selectively connecting the first reference voltage to the output node of the controllable voltage divider. The first pull-down circuit is coupled to the output node of the controllable voltage divider and the second reference voltage, and is utilized for selectively connecting the second reference voltage to the output node of the controllable voltage divider.